Configuring and using network file services

Red Hat Enterprise Linux 9

A guide to configuring and using network file services in Red Hat Enterprise Linux 9.

Red Hat Customer Content Services

Abstract

This document describes how to configure and run network file services on Red Hat Enterprise Linux 9, including Samba server and NFS server.

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Chapter 1. Using Samba as a server

Samba implements the Server Message Block (SMB) protocol in Red Hat Enterprise Linux. The SMB protocol is used to access resources on a server, such as file shares and shared printers. Additionally, Samba implements the Distributed Computing Environment Remote Procedure Call (DCE RPC) protocol used by Microsoft Windows.

You can run Samba as:

  • An Active Directory (AD) or NT4 domain member
  • A standalone server

  • An NT4 Primary Domain Controller (PDC) or Backup Domain Controller (BDC)

    Note

    Red Hat supports the PDC and BDC modes only in existing installations with Windows versions which support NT4 domains. Red Hat recommends not setting up a new Samba NT4 domain, because Microsoft operating systems later than Windows 7 and Windows Server 2008 R2 do not support NT4 domains.

    Red Hat does not support running Samba as an AD domain controller (DC).

Independently of the installation mode, you can optionally share directories and printers. This enables Samba to act as a file and print server.

1.1. Understanding the different Samba services and modes

This section describes the different services included in Samba and the different modes you can configure.

1.1.1. The Samba services

Samba provides the following services:

smbd

This service provides file sharing and printing services using the SMB protocol. Additionally, the service is responsible for resource locking and for authenticating connecting users. For authenticating domain members, smbd requires winbindd. The smb systemd service starts and stops the smbd daemon.

To use the smbd service, install the samba package.

nmbd

This service provides host name and IP resolution using the NetBIOS over IPv4 protocol. Additionally to the name resolution, the nmbd service enables browsing the SMB network to locate domains, work groups, hosts, file shares, and printers. For this, the service either reports this information directly to the broadcasting client or forwards it to a local or master browser. The nmb systemd service starts and stops the nmbd daemon.

Note that modern SMB networks use DNS to resolve clients and IP addresses. For Kerberos a working DNS setup is required.

To use the nmbd service, install the samba package.

winbindd

This service provides an interface for the Name Service Switch (NSS) to use AD or NT4 domain users and groups on the local system. This enables, for example, domain users to authenticate to services hosted on a Samba server or to other local services. The winbind systemd service starts and stops the winbindd daemon.

If you set up Samba as a domain member, winbindd must be started before the smbd service. Otherwise, domain users and groups are not available to the local system..

To use the winbindd service, install the samba-winbind package.

Important

Red Hat only supports running Samba as a server with the winbindd service to provide domain users and groups to the local system. Due to certain limitations, such as missing Windows access control list (ACL) support and NT LAN Manager (NTLM) fallback, SSSD is not supported.

1.1.2. The Samba security services

The security parameter in the [global] section in the /etc/samba/smb.conf file manages how Samba authenticates users that are connecting to the service. Depending on the mode you install Samba in, the parameter must be set to different values:

On an AD domain member, set security = ads

In this mode, Samba uses Kerberos to authenticate AD users.

For details about setting up Samba as a domain member, see Setting up Samba as an AD domain member server.

On a standalone server, set security = user

In this mode, Samba uses a local database to authenticate connecting users.

For details about setting up Samba as a standalone server, see Setting up Samba as a standalone server.

On an NT4 PDC or BDC, set security = user
In this mode, Samba authenticates users to a local or LDAP database.
On an NT4 domain member, set security = domain

In this mode, Samba authenticates connecting users to an NT4 PDC or BDC. You cannot use this mode on AD domain members.

For details about setting up Samba as a domain member, see Setting up Samba as an AD domain member server.

Additional resources

  • security parameter in the smb.conf(5) man page

1.1.3. Scenarios when Samba services and Samba client utilities load and reload their configuration

The following describes when Samba services and utilities load and reload their configuration:

  • Samba services reload their configuration:

    • Automatically every 3 minutes
    • On manual request, for example, when you run the smbcontrol all reload-config command.
  • Samba client utilities read their configuration only when you start them.

Note that certain parameters, such as security require a restart of the smb service to take effect and a reload is not sufficient.

Additional resources

  • The How configuration changes are applied section in the smb.conf(5) man page
  • The smbd(8), nmbd(8), and winbindd(8) man pages

1.1.4. Editing the Samba configuration in a safe way

Samba services automatically reload their configuration every 3 minutes. This procedure describes how to edit the Samba configuration in a way that prevents the services reload the changes before you have verified the configuration using the testparm utility.

Prerequisites

  • Samba is installed.

Procedure

  1. Create a copy of the /etc/samba/smb.conf file: 

    # cp /etc/samba/smb.conf /etc/samba/samba.conf.copy
  2. Edit the copied file and make the desired changes.

  3. Verify the configuration in the /etc/samba/samba.conf.copy file: 

    # testparm -s /etc/samba/samba.conf.copy

    If testparm reports errors, fix them and run the command again.

  4. Override the /etc/samba/smb.conf file with the new configuration: 

    # mv /etc/samba/samba.conf.copy /etc/samba/smb.conf

  5. Wait until the Samba services automatically reload their configuration or manually reload the configuration: 

    # smbcontrol all reload-config

Additional resources

1.2. Verifying the smb.conf file by using the testparm utility

The testparm utility verifies that the Samba configuration in the /etc/samba/smb.conf file is correct. The utility detects invalid parameters and values, but also incorrect settings, such as for ID mapping. If testparm reports no problem, the Samba services will successfully load the /etc/samba/smb.conf file. Note that testparm cannot verify that the configured services will be available or work as expected.

Important

Red Hat recommends that you verify the /etc/samba/smb.conf file by using testparm after each modification of this file.

Prerequisites

  • You installed Samba.
  • The /etc/samba/smb.conf file exits.

Procedure

  1. Run the testparm utility as the root user: 

    # testparm
Load smb config files from /etc/samba/smb.conf
rlimit_max: increasing rlimit_max (1024) to minimum Windows limit (16384)
Unknown parameter encountered: "log levell"
Processing section "[example_share]"
Loaded services file OK.
ERROR: The idmap range for the domain * (tdb) overlaps with the range of DOMAIN (ad)!

Server role: ROLE_DOMAIN_MEMBER

Press enter to see a dump of your service definitions

# Global parameters
[global]
	...

[example_share]
	...

    The previous example output reports a non-existent parameter and an incorrect ID mapping configuration.

  2. If testparm reports incorrect parameters, values, or other errors in the configuration, fix the problem and run the utility again.

1.3. Setting up Samba as a standalone server

You can set up Samba as a server that is not a member of a domain. In this installation mode, Samba authenticates users to a local database instead of to a central DC. Additionally, you can enable guest access to allow users to connect to one or multiple services without authentication.

1.3.1. Setting up the server configuration for the standalone server

This section describes how to set up the server configuration for a Samba standalone server.

Procedure

  1. Install the samba package: 

    # dnf install samba

  2. Edit the /etc/samba/smb.conf file and set the following parameters: 

    [global]
	workgroup = Example-WG
	netbios name = Server
	security = user

	log file = /var/log/samba/%m.log
	log level = 1

    This configuration defines a standalone server named Server within the Example-WG work group. Additionally, this configuration enables logging on a minimal level (1) and log files will be stored in the /var/log/samba/ directory. Samba will expand the %m macro in the log file parameter to the NetBIOS name of connecting clients. This enables individual log files for each client.

  3. Optionally, configure file or printer sharing. See:

  4. Verify the /etc/samba/smb.conf file: 

    # testparm

  5. If you set up shares that require authentication, create the user accounts.

    For details, see Creating and enabling local user accounts.

  6. Open the required ports and reload the firewall configuration by using the firewall-cmd utility: 

    # firewall-cmd --permanent --add-service=samba
# firewall-cmd --reload

  7. Enable and start the smb service: 

    # systemctl enable --now smb

Additional resources

  • smb.conf(5) man page

1.3.2. Creating and enabling local user accounts

To enable users to authenticate when they connect to a share, you must create the accounts on the Samba host both in the operating system and in the Samba database. Samba requires the operating system account to validate the Access Control Lists (ACL) on file system objects and the Samba account to authenticate connecting users.

If you use the passdb backend = tdbsam default setting, Samba stores user accounts in the /var/lib/samba/private/passdb.tdb database.

The procedure in this section describes how to create a local Samba user named example.

Prerequisites

  • Samba is installed and configured as a standalone server.

Procedure

  1. Create the operating system account: 

    # useradd -M -s /sbin/nologin example

    This command adds the example account without creating a home directory. If the account is only used to authenticate to Samba, assign the /sbin/nologin command as shell to prevent the account from logging in locally.

  2. Set a password to the operating system account to enable it: 

    # passwd example
Enter new UNIX password: password
Retype new UNIX password: password
passwd: password updated successfully

    Samba does not use the password set on the operating system account to authenticate. However, you need to set a password to enable the account. If an account is disabled, Samba denies access if this user connects.

  3. Add the user to the Samba database and set a password to the account: 

    # smbpasswd -a example
New SMB password: password
Retype new SMB password: password
Added user example.

    Use this password to authenticate when using this account to connect to a Samba share.

  4. Enable the Samba account: 

    # smbpasswd -e example
Enabled user example.

1.4. Understanding and configuring Samba ID mapping

Windows domains distinguish users and groups by unique Security Identifiers (SID). However, Linux requires unique UIDs and GIDs for each user and group. If you run Samba as a domain member, the winbindd service is responsible for providing information about domain users and groups to the operating system.

To enable the winbindd service to provide unique IDs for users and groups to Linux, you must configure ID mapping in the /etc/samba/smb.conf file for:

  • The local database (default domain)
  • The AD or NT4 domain the Samba server is a member of
  • Each trusted domain from which users must be able to access resources on this Samba server

Samba provides different ID mapping back ends for specific configurations. The most frequently used back ends are:

Back endUse case

tdb

The * default domain only

ad

AD domains only

rid

AD and NT4 domains

autorid

AD, NT4, and the * default domain

1.4.1. Planning Samba ID ranges

Regardless of whether you store the Linux UIDs and GIDs in AD or if you configure Samba to generate them, each domain configuration requires a unique ID range that must not overlap with any of the other domains.

Warning

If you set overlapping ID ranges, Samba fails to work correctly.

Example 1.1. Unique ID Ranges

The following shows non-overlapping ID mapping ranges for the default (*), AD-DOM, and the TRUST-DOM domains. 

[global]
...
idmap config * : backend = tdb
idmap config * : range = 10000-999999

idmap config AD-DOM:backend = rid
idmap config AD-DOM:range = 2000000-2999999

idmap config TRUST-DOM:backend = rid
idmap config TRUST-DOM:range = 4000000-4999999
Important

You can only assign one range per domain. Therefore, leave enough space between the domains ranges. This enables you to extend the range later if your domain grows.

If you later assign a different range to a domain, the ownership of files and directories previously created by these users and groups will be lost.

1.4.2. The * default domain

In a domain environment, you add one ID mapping configuration for each of the following:

  • The domain the Samba server is a member of
  • Each trusted domain that should be able to access the Samba server

However, for all other objects, Samba assigns IDs from the default domain. This includes:

  • Local Samba users and groups
  • Samba built-in accounts and groups, such as BUILTIN\Administrators
Important

You must configure the default domain as described in this section to enable Samba to operate correctly.

The default domain back end must be writable to permanently store the assigned IDs.

For the default domain, you can use one of the following back ends:

tdb

When you configure the default domain to use the tdb back end, set an ID range that is big enough to include objects that will be created in the future and that are not part of a defined domain ID mapping configuration.

For example, set the following in the [global] section in the /etc/samba/smb.conf file: 

idmap config * : backend = tdb
idmap config * : range = 10000-999999

For further details, see Using the TDB ID mapping back end.

autorid

When you configure the default domain to use the autorid back end, adding additional ID mapping configurations for domains is optional.

For example, set the following in the [global] section in the /etc/samba/smb.conf file: 

idmap config * : backend = autorid
idmap config * : range = 10000-999999

For further details, see Using the autorid ID mapping back end.

1.4.3. Using the tdb ID mapping back end

The winbindd service uses the writable tdb ID mapping back end by default to store Security Identifier (SID), UID, and GID mapping tables. This includes local users, groups, and built-in principals.

Use this back end only for the * default domain. For example: 

idmap config * : backend = tdb
idmap config * : range = 10000-999999

Additional resources

1.4.4. Using the ad ID mapping back end

This section describes how to configure a Samba AD member to use the ad ID mapping back end.

The ad ID mapping back end implements a read-only API to read account and group information from AD. This provides the following benefits:

  • All user and group settings are stored centrally in AD.
  • User and group IDs are consistent on all Samba servers that use this back end.
  • The IDs are not stored in a local database which can corrupt, and therefore file ownerships cannot be lost.
Note

The ad ID mapping back end does not support Active Directory domains with one-way trusts. If you configure a domain member in an Active Directory with one-way trusts, use instead one of the following ID mapping back ends: tdb, rid, or autorid.

The ad back end reads the following attributes from AD:

AD attribute nameObject typeMapped to

sAMAccountName

User and group

User or group name, depending on the object

uidNumber

User

User ID (UID)

gidNumber

Group

Group ID (GID)

loginShell [a]

User

Path to the shell of the user

unixHomeDirectory [a]

User

Path to the home directory of the user

primaryGroupID [b]

User

Primary group ID

[a] Samba only reads this attribute if you set idmap config DOMAIN:unix_nss_info = yes.
[b] Samba only reads this attribute if you set idmap config DOMAIN:unix_primary_group = yes.

Prerequisites

  • Both users and groups must have unique IDs set in AD, and the IDs must be within the range configured in the /etc/samba/smb.conf file. Objects whose IDs are outside of the range will not be available on the Samba server.
  • Users and groups must have all required attributes set in AD. If required attributes are missing, the user or group will not be available on the Samba server. The required attributes depend on your configuration. .Prerequisites
  • You installed Samba.
  • The Samba configuration, except ID mapping, exists in the /etc/samba/smb.conf file.

Procedure

  1. Edit the [global] section in the /etc/samba/smb.conf file:

    1. Add an ID mapping configuration for the default domain (*) if it does not exist. For example: 

      idmap config * : backend = tdb
idmap config * : range = 10000-999999

    2. Enable the ad ID mapping back end for the AD domain: 

      idmap config DOMAIN : backend = ad

    3. Set the range of IDs that is assigned to users and groups in the AD domain. For example: 

      idmap config DOMAIN : range = 2000000-2999999
      Important

      The range must not overlap with any other domain configuration on this server. Additionally, the range must be set big enough to include all IDs assigned in the future. For further details, see Planning Samba ID ranges.

    4. Set that Samba uses the RFC 2307 schema when reading attributes from AD: 

      idmap config DOMAIN : schema_mode = rfc2307

    5. To enable Samba to read the login shell and the path to the users home directory from the corresponding AD attribute, set: 

      idmap config DOMAIN : unix_nss_info = yes

      Alternatively, you can set a uniform domain-wide home directory path and login shell that is applied to all users. For example: 

      template shell = /bin/bash
template homedir = /home/%U

    6. By default, Samba uses the primaryGroupID attribute of a user object as the user’s primary group on Linux. Alternatively, you can configure Samba to use the value set in the gidNumber attribute instead: 

      idmap config DOMAIN : unix_primary_group = yes

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

  • The * default domain
  • smb.conf(5) and idmap_ad(8) man pages
  • VARIABLE SUBSTITUTIONS section in the smb.conf(5) man page

1.4.5. Using the rid ID mapping back end

This section describes how to configure a Samba domain member to use the rid ID mapping back end.

Samba can use the relative identifier (RID) of a Windows SID to generate an ID on Red Hat Enterprise Linux.

Note

The RID is the last part of a SID. For example, if the SID of a user is S-1-5-21-5421822485-1151247151-421485315-30014, then 30014 is the corresponding RID.

The rid ID mapping back end implements a read-only API to calculate account and group information based on an algorithmic mapping scheme for AD and NT4 domains. When you configure the back end, you must set the lowest and highest RID in the idmap config DOMAIN : range parameter. Samba will not map users or groups with a lower or higher RID than set in this parameter.

Important

As a read-only back end, rid cannot assign new IDs, such as for BUILTIN groups. Therefore, do not use this back end for the * default domain.

Benefits of using the rid back end

  • All domain users and groups that have an RID within the configured range are automatically available on the domain member.
  • You do not need to manually assign IDs, home directories, and login shells.

Drawbacks of using the rid back end

  • All domain users get the same login shell and home directory assigned. However, you can use variables.
  • User and group IDs are only the same across Samba domain members if all use the rid back end with the same ID range settings.
  • You cannot exclude individual users or groups from being available on the domain member. Only users and groups outside of the configured range are excluded.
  • Based on the formulas the winbindd service uses to calculate the IDs, duplicate IDs can occur in multi-domain environments if objects in different domains have the same RID.

Prerequisites

  • You installed Samba.
  • The Samba configuration, except ID mapping, exists in the /etc/samba/smb.conf file.

Procedure

  1. Edit the [global] section in the /etc/samba/smb.conf file:

    1. Add an ID mapping configuration for the default domain (*) if it does not exist. For example: 

      idmap config * : backend = tdb
idmap config * : range = 10000-999999

    2. Enable the rid ID mapping back end for the domain: 

      idmap config DOMAIN : backend = rid

    3. Set a range that is big enough to include all RIDs that will be assigned in the future. For example: 

      idmap config DOMAIN : range = 2000000-2999999

      Samba ignores users and groups whose RIDs in this domain are not within the range.

      Important

      The range must not overlap with any other domain configuration on this server. Additionally, the range must be set big enough to include all IDs assigned in the future. For further details, see Planning Samba ID ranges.

    4. Set a shell and home directory path that will be assigned to all mapped users. For example: 

      template shell = /bin/bash
template homedir = /home/%U

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

  • The * default domain
  • VARIABLE SUBSTITUTIONS section in the smb.conf(5) man page
  • Calculation of the local ID from a RID, see the idmap_rid(8) man page

1.4.6. Using the autorid ID mapping back end

This section describes how to configure a Samba domain member to use the autorid ID mapping back end.

The autorid back end works similar to the rid ID mapping back end, but can automatically assign IDs for different domains. This enables you to use the autorid back end in the following situations:

  • Only for the * default domain
  • For the * default domain and additional domains, without the need to create ID mapping configurations for each of the additional domains
  • Only for specific domains
Note

If you use autorid for the default domain, adding additional ID mapping configuration for domains is optional.

Parts of this section were adopted from the idmap config autorid documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

Benefits of using the autorid back end

  • All domain users and groups whose calculated UID and GID is within the configured range are automatically available on the domain member.
  • You do not need to manually assign IDs, home directories, and login shells.
  • No duplicate IDs, even if multiple objects in a multi-domain environment have the same RID.

Drawbacks

  • User and group IDs are not the same across Samba domain members.
  • All domain users get the same login shell and home directory assigned. However, you can use variables.
  • You cannot exclude individual users or groups from being available on the domain member. Only users and groups whose calculated UID or GID is outside of the configured range are excluded.

Prerequisites

  • You installed Samba.
  • The Samba configuration, except ID mapping, exists in the /etc/samba/smb.conf file.

Procedure

  1. Edit the [global] section in the /etc/samba/smb.conf file:

    1. Enable the autorid ID mapping back end for the * default domain: 

      idmap config * : backend = autorid

    2. Set a range that is big enough to assign IDs for all existing and future objects. For example: 

      idmap config * : range = 10000-999999

      Samba ignores users and groups whose calculated IDs in this domain are not within the range.

      Warning

      After you set the range and Samba starts using it, you can only increase the upper limit of the range. Any other change to the range can result in new ID assignments, and thus in losing file ownerships.

    3. Optionally, set a range size. For example: 

      idmap config * : rangesize = 200000

      Samba assigns this number of continuous IDs for each domain’s object until all IDs from the range set in the idmap config * : range parameter are taken.

      Note

      If you set a rangesize, you need to adapt the range accordingly. The range needs to be a multiple of the rangesize.

    4. Set a shell and home directory path that will be assigned to all mapped users. For example: 

      template shell = /bin/bash
template homedir = /home/%U

    5. Optionally, add additional ID mapping configuration for domains. If no configuration for an individual domain is available, Samba calculates the ID using the autorid back end settings in the previously configured * default domain.

      Important

      The range must not overlap with any other domain configuration on this server. Additionally, the range must be set big enough to include all IDs assigned in the future. For further details, see Planning Samba ID ranges.

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

  • THE MAPPING FORMULAS section in the idmap_autorid(8) man page
  • rangesize parameter description in the idmap_autorid(8) man page
  • VARIABLE SUBSTITUTIONS section in the smb.conf(5) man page

1.5. Setting up Samba as an AD domain member server

If you are running an AD or NT4 domain, use Samba to add your Red Hat Enterprise Linux server as a member to the domain to gain the following:

  • Access domain resources on other domain members
  • Authenticate domain users to local services, such as sshd
  • Share directories and printers hosted on the server to act as a file and print server

1.5.1. Joining a RHEL system to an AD domain

Samba Winbind is an alternative to the System Security Services Daemon (SSSD) for connecting a Red Hat Enterprise Linux (RHEL) system with Active Directory (AD). This section describes how to join a RHEL system to an AD domain by using realmd to configure Samba Winbind.

Procedure

  1. If your AD requires the deprecated RC4 encryption type for Kerberos authentication, enable support for these ciphers in RHEL: 

    # update-crypto-policies --set DEFAULT:AD-SUPPORT

  2. Install the following packages: 

    # dnf install realmd oddjob-mkhomedir oddjob samba-winbind-clients \
       samba-winbind samba-common-tools samba-winbind-krb5-locator

  3. To share directories or printers on the domain member, install the samba package: 

    # dnf install samba

  4. Backup the existing /etc/samba/smb.conf Samba configuration file: 

    # mv /etc/samba/smb.conf /etc/samba/smb.conf.bak

  5. Join the domain. For example, to join a domain named ad.example.com: 

    # realm join --membership-software=samba --client-software=winbind ad.example.com

    Using the previous command, the realm utility automatically:

    • Creates a /etc/samba/smb.conf file for a membership in the ad.example.com domain
    • Adds the winbind module for user and group lookups to the /etc/nsswitch.conf file
    • Updates the Pluggable Authentication Module (PAM) configuration files in the /etc/pam.d/ directory
    • Starts the winbind service and enables the service to start when the system boots
  6. Optionally, set an alternative ID mapping back end or customized ID mapping settings in the /etc/samba/smb.conf file.

For details, see Understanding and configuring Samba ID mapping.

  1. Verify that the winbind service is running: 

    # systemctl status winbind
...
   Active: active (running) since Tue 2018-11-06 19:10:40 CET; 15s ago
    Important

    To enable Samba to query domain user and group information, the winbind service must be running before you start smb.

  2. If you installed the samba package to share directories and printers, enable and start the smb service: 

    # systemctl enable --now smb
  3. Optionally, if you are authenticating local logins to Active Directory, enable the winbind_krb5_localauth plug-in. See Using the local authorization plug-in for MIT Kerberos.

Verification steps

  1. Display an AD user’s details, such as the AD administrator account in the AD domain: 

    # getent passwd "AD\administrator"
AD\administrator:*:10000:10000::/home/administrator@AD:/bin/bash

  2. Query the members of the domain users group in the AD domain: 

    # getent group "AD\Domain Users"
    AD\domain users:x:10000:user1,user2

  3. Optionally, verify that you can use domain users and groups when you set permissions on files and directories. For example, to set the owner of the /srv/samba/example.txt file to AD\administrator and the group to AD\Domain Users: 

    # chown "AD\administrator":"AD\Domain Users" /srv/samba/example.txt

  4. Verify that Kerberos authentication works as expected:

    1. On the AD domain member, obtain a ticket for the administrator@AD.EXAMPLE.COM principal: 

      # kinit administrator@AD.EXAMPLE.COM

    2. Display the cached Kerberos ticket: 

      # klist
Ticket cache: KCM:0
Default principal: administrator@AD.EXAMPLE.COM

Valid starting       Expires              Service principal
01.11.2018 10:00:00  01.11.2018 20:00:00  krbtgt/AD.EXAMPLE.COM@AD.EXAMPLE.COM
        renew until 08.11.2018 05:00:00

  5. Display the available domains: 

    # wbinfo --all-domains
BUILTIN
SAMBA-SERVER
AD

Additional resources

1.5.2. Using the local authorization plug-in for MIT Kerberos

The winbind service provides Active Directory users to the domain member. In certain situations, administrators want to enable domain users to authenticate to local services, such as an SSH server, which are running on the domain member. When using Kerberos to authenticate the domain users, enable the winbind_krb5_localauth plug-in to correctly map Kerberos principals to Active Directory accounts through the winbind service.

For example, if the sAMAccountName attribute of an Active Directory user is set to EXAMPLE and the user tries to log with the user name lowercase, Kerberos returns the user name in upper case. As a consequence, the entries do not match and authentication fails.

Using the winbind_krb5_localauth plug-in, the account names are mapped correctly. Note that this only applies to GSSAPI authentication and not for getting the initial ticket granting ticket (TGT).

Prerequisites

  • Samba is configured as a member of an Active Directory.
  • Red Hat Enterprise Linux authenticates log in attempts against Active Directory.
  • The winbind service is running.

Procedure

Edit the /etc/krb5.conf file and add the following section: 

[plugins]
localauth = {
     module = winbind:/usr/lib64/samba/krb5/winbind_krb5_localauth.so
     enable_only = winbind
}

Additional resources

  • winbind_krb5_localauth(8) man page.

1.6. Setting up Samba on an IdM domain member

This section describes how to set up Samba on a host that is joined to a Red Hat Identity Management (IdM) domain. Users from IdM and also, if available, from trusted Active Directory (AD) domains, can access shares and printer services provided by Samba.

Important

Using Samba on an IdM domain member is an unsupported Technology Preview feature and contains certain limitations. For example, IdM trust controllers do not support the Active Directory Global Catalog service, and they do not support resolving IdM groups using the Distributed Computing Environment / Remote Procedure Calls (DCE/RPC) protocols. As a consequence, AD users can only access Samba shares and printers hosted on IdM clients when logged in to other IdM clients; AD users logged into a Windows machine can not access Samba shares hosted on an IdM domain member.

Customers deploying Samba on IdM domain members are encouraged to provide feedback to Red Hat.

Prerequisites

  • The host is joined as a client to the IdM domain.
  • Both the IdM servers and the client must run on RHEL 9.0 or later.

1.6.1. Preparing the IdM domain for installing Samba on domain members

Before you can set up Samba on an IdM client, you must prepare the IdM domain using the ipa-adtrust-install utility on an IdM server.

Note

Any system where you run the ipa-adtrust-install command automatically becomes an AD trust controller. However, you must run ipa-adtrust-install only once on an IdM server.

Prerequisites

  • IdM server is installed.
  • You need root privileges to install packages and restart IdM services.

Procedure

  1. Install the required packages: 

    [root@ipaserver ~]# dnf install ipa-server-trust-ad samba-client

  2. Authenticate as the IdM administrative user: 

    [root@ipaserver ~]# kinit admin

  3. Run the ipa-adtrust-install utility: 

    [root@ipaserver ~]# ipa-adtrust-install

    The DNS service records are created automatically if IdM was installed with an integrated DNS server.

    If you installed IdM without an integrated DNS server, ipa-adtrust-install prints a list of service records that you must manually add to DNS before you can continue.

  4. The script prompts you that the /etc/samba/smb.conf already exists and will be rewritten: 

    WARNING: The smb.conf already exists. Running ipa-adtrust-install will break your existing Samba configuration.

Do you wish to continue? [no]: yes

  5. The script prompts you to configure the slapi-nis plug-in, a compatibility plug-in that allows older Linux clients to work with trusted users: 

    Do you want to enable support for trusted domains in Schema Compatibility plugin?
This will allow clients older than SSSD 1.9 and non-Linux clients to work with trusted users.

Enable trusted domains support in slapi-nis? [no]: yes

  6. When prompted, enter the NetBIOS name for the IdM domain or press Enter to accept the name suggested: 

    Trust is configured but no NetBIOS domain name found, setting it now.
Enter the NetBIOS name for the IPA domain.
Only up to 15 uppercase ASCII letters, digits and dashes are allowed.
Example: EXAMPLE.

NetBIOS domain name [IDM]:

  7. You are prompted to run the SID generation task to create a SID for any existing users: 

    Do you want to run the ipa-sidgen task? [no]: yes

    This is a resource-intensive task, so if you have a high number of users, you can run this at another time.

  8. (Optional) By default, the Dynamic RPC port range is defined as 49152-65535 for Windows Server 2008 and later. If you need to define a different Dynamic RPC port range for your environment, configure Samba to use different ports and open those ports in your firewall settings. The following example sets the port range to 55000-65000. 

    [root@ipaserver ~]# net conf setparm global 'rpc server dynamic port range' 55000-65000
[root@ipaserver ~]# firewall-cmd --add-port=55000-65000/tcp
[root@ipaserver ~]# firewall-cmd --runtime-to-permanent

  9. Restart the ipa service: 

    [root@ipaserver ~]# ipactl restart

  10. Use the smbclient utility to verify that Samba responds to Kerberos authentication from the IdM side: 

    [root@ipaserver ~]# smbclient -L server.idm.example.com -U user_name --use-kerberos=required
lp_load_ex: changing to config backend registry
    Sharename       Type      Comment
    ---------       ----      -------
    IPC$            IPC       IPC Service (Samba 4.15.2)
...

1.6.2. Enabling the AES encryption type in Active Directory using a GPO

This section describes how to enable the AES encryption type in Active Directory (AD) using a group policy object (GPO). Certain features on RHEL, such as running a Samba server on an IdM client, require this encryption type.

Note that RHEL no longer supports the weak DES and RC4 encryption types.

Prerequisites

  • You are logged into AD as a user who can edit group policies.
  • The Group Policy Management Console is installed on the computer.

Procedure

  1. Open the Group Policy Management Console.
  2. Right-click Default Domain Policy, and select Edit. The Group Policy Management Editor opens.
  3. Navigate to Computer Configuration → Policies → Windows Settings → Security Settings → Local Policies → Security Options.
  4. Double-click the Network security: Configure encryption types allowed for Kerberos policy.
  5. Select AES256_HMAC_SHA1 and, optionally, Future encryption types.
  6. Click OK.
  7. Close the Group Policy Management Editor.
  8. Repeat the steps for the Default Domain Controller Policy.

  9. Wait until the Windows domain controllers (DC) applied the group policy automatically. Alternatively, to apply the GPO manually on a DC, enter the following command using an account that has administrator permissions: 

    C:\> gpupdate /force /target:computer

1.6.3. Installing and configuring a Samba server on an IdM client

This section describes how to install and configure Samba on a client enrolled in an IdM domain.

Prerequisites

Procedure

  1. Install the ipa-client-samba package: 

    [root@idm_client]# dnf install ipa-client-samba

  2. Use the ipa-client-samba utility to prepare the client and create an initial Samba configuration: 

    [root@idm_client]# ipa-client-samba
Searching for IPA server...
IPA server: DNS discovery
Chosen IPA master: idm_server.idm.example.com
SMB principal to be created: cifs/idm_client.idm.example.com@IDM.EXAMPLE.COM
NetBIOS name to be used: IDM_CLIENT
Discovered domains to use:

 Domain name: idm.example.com
NetBIOS name: IDM
         SID: S-1-5-21-525930803-952335037-206501584
    ID range: 212000000 - 212199999

 Domain name: ad.example.com
NetBIOS name: AD
         SID: None
    ID range: 1918400000 - 1918599999

Continue to configure the system with these values? [no]: yes
Samba domain member is configured. Please check configuration at /etc/samba/smb.conf and start smb and winbind services

  3. By default, ipa-client-samba automatically adds the [homes] section to the /etc/samba/smb.conf file that dynamically shares a user’s home directory when the user connects. If users do not have home directories on this server, or if you do not want to share them, remove the following lines from /etc/samba/smb.conf: 

    [homes]
    read only = no

  4. Share directories and printers. For details, see:

  5. Open the ports required for a Samba client in the local firewall: 

    [root@idm_client]# firewall-cmd --permanent --add-service=samba-client
[root@idm_client]# firewall-cmd --reload

  6. Enable and start the smb and winbind services: 

    [root@idm_client]# systemctl enable --now smb winbind

Verification steps

Run the following verification step on a different IdM domain member that has the samba-client package installed:

  • List the shares on the Samba server using Kerberos authentication: 

    $ smbclient -L idm_client.idm.example.com -U user_name --use-kerberos=required
lp_load_ex: changing to config backend registry

    Sharename       Type      Comment
    ---------       ----      -------
    example         Disk
    IPC$            IPC       IPC Service (Samba 4.15.2)
...

Additional resources

  • ipa-client-samba(1) man page

1.6.4. Manually adding an ID mapping configuration if IdM trusts a new domain

Samba requires an ID mapping configuration for each domain from which users access resources. On an existing Samba server running on an IdM client, you must manually add an ID mapping configuration after the administrator added a new trust to an Active Directory (AD) domain.

Prerequisites

  • You configured Samba on an IdM client. Afterward, a new trust was added to IdM.
  • The DES and RC4 encryption types for Kerberos must be disabled in the trusted AD domain. For security reasons, RHEL 9 does not support these weak encryption types.

Procedure

  1. Authenticate using the host’s keytab: 

    [root@idm_client]# kinit -k

  2. Use the ipa idrange-find command to display both the base ID and the ID range size of the new domain. For example, the following command displays the values for the ad.example.com domain: 

    [root@idm_client]# ipa idrange-find --name="AD.EXAMPLE.COM_id_range" --raw
---------------
1 range matched
---------------
  cn: AD.EXAMPLE.COM_id_range
  ipabaseid: 1918400000
  ipaidrangesize: 200000
  ipabaserid: 0
  ipanttrusteddomainsid: S-1-5-21-968346183-862388825-1738313271
  iparangetype: ipa-ad-trust
----------------------------
Number of entries returned 1
----------------------------

    You need the values from the ipabaseid and ipaidrangesize attributes in the next steps.

  3. To calculate the highest usable ID, use the following formula: 

    maximum_range = ipabaseid + ipaidrangesize - 1

    With the values from the previous step, the highest usable ID for the ad.example.com domain is 1918599999 (1918400000 + 200000 - 1).

  4. Edit the /etc/samba/smb.conf file, and add the ID mapping configuration for the domain to the [global] section: 

    idmap config AD : range = 1918400000 - 1918599999
idmap config AD : backend = sss

    Specify the value from ipabaseid attribute as the lowest and the computed value from the previous step as the highest value of the range.

  5. Restart the smb and winbind services: 

    [root@idm_client]# systemctl restart smb winbind

Verification steps

  • List the shares on the Samba server using Kerberos authentication: 

    $ smbclient -L idm_client.idm.example.com -U user_name --use-kerberos=required
lp_load_ex: changing to config backend registry

    Sharename       Type      Comment
    ---------       ----      -------
    example         Disk
    IPC$            IPC       IPC Service (Samba 4.15.2)
...

1.6.5. Additional resources

1.7. Setting up a Samba file share that uses POSIX ACLs

As a Linux service, Samba supports shares with POSIX ACLs. They enable you to manage permissions locally on the Samba server using utilities, such as chmod. If the share is stored on a file system that supports extended attributes, you can define ACLs with multiple users and groups.

Note

If you need to use fine-granular Windows ACLs instead, see Setting up a share that uses Windows ACLs.

Parts of this section were adopted from the Setting up a Share Using POSIX ACLs documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

1.7.1. Adding a share that uses POSIX ACLs

This section describes how to create a share named example that provides the content of the /srv/samba/example/ directory, and uses POSIX ACLs.

Prerequisites

Samba has been set up in one of the following modes:

Procedure

  1. Create the folder if it does not exist. For example: 

    # mkdir -p /srv/samba/example/

  2. If you run SELinux in enforcing mode, set the samba_share_t context on the directory: 

    # semanage fcontext -a -t samba_share_t "/srv/samba/example(/.*)?"
# restorecon -Rv /srv/samba/example/

  3. Set file system ACLs on the directory. For details, see:

  4. Add the example share to the /etc/samba/smb.conf file. For example, to add the share write-enabled: 

    [example]
	path = /srv/samba/example/
	read only = no
    Note

    Regardless of the file system ACLs; if you do not set read only = no, Samba shares the directory in read-only mode.

  5. Verify the /etc/samba/smb.conf file: 

    # testparm

  6. Open the required ports and reload the firewall configuration using the firewall-cmd utility: 

    # firewall-cmd --permanent --add-service=samba
# firewall-cmd --reload

  7. Restart the smb service: 

    # systemctl restart smb

1.7.2. Setting standard Linux ACLs on a Samba share that uses POSIX ACLs

The standard ACLs on Linux support setting permissions for one owner, one group, and for all other undefined users. You can use the chown, chgrp, and chmod utility to update the ACLs. If you require precise control, then you use the more complex POSIX ACLs, see

Setting extended ACLs on a Samba share that uses POSIX ACLs.

The following procedure sets the owner of the /srv/samba/example/ directory to the root user, grants read and write permissions to the Domain Users group, and denies access to all other users.

Prerequisites

  • The Samba share on which you want to set the ACLs exists.

Procedure

# chown root:"Domain Users" /srv/samba/example/
# chmod 2770 /srv/samba/example/

Note

Enabling the set-group-ID (SGID) bit on a directory automatically sets the default group for all new files and subdirectories to that of the directory group, instead of the usual behavior of setting it to the primary group of the user who created the new directory entry.

Additional resources

  • chown(1) and chmod(1) man pages

1.7.3. Setting extended ACLs on a Samba share that uses POSIX ACLs

If the file system the shared directory is stored on supports extended ACLs, you can use them to set complex permissions. Extended ACLs can contain permissions for multiple users and groups.

Extended POSIX ACLs enable you to configure complex ACLs with multiple users and groups. However, you can only set the following permissions:

  • No access
  • Read access
  • Write access
  • Full control

If you require the fine-granular Windows permissions, such as Create folder / append data, configure the share to use Windows ACLs.

See Setting up a share that uses Windows ACLs.

The following procedure shows how to enable extended ACLs on a share. Additionally, it contains an example about setting extended ACLs.

Prerequisites

  • The Samba share on which you want to set the ACLs exists.

Procedure

  1. Enable the following parameter in the share’s section in the /etc/samba/smb.conf file to enable ACL inheritance of extended ACLs: 

    inherit acls = yes

    For details, see the parameter description in the smb.conf(5) man page.

  2. Restart the smb service: 

    # systemctl restart smb

  3. Set the ACLs on the directory. For example:

    Example 1.2. Setting Extended ACLs

    The following procedure sets read, write, and execute permissions for the Domain Admins group, read, and execute permissions for the Domain Users group, and deny access to everyone else on the /srv/samba/example/ directory:

    1. Disable auto-granting permissions to the primary group of user accounts: 

      # setfacl -m group::--- /srv/samba/example/
# setfacl -m default:group::--- /srv/samba/example/

      The primary group of the directory is additionally mapped to the dynamic CREATOR GROUP principal. When you use extended POSIX ACLs on a Samba share, this principal is automatically added and you cannot remove it.

    2. Set the permissions on the directory:

      1. Grant read, write, and execute permissions to the Domain Admins group: 

        # setfacl -m group:"DOMAIN\Domain Admins":rwx /srv/samba/example/

      2. Grant read and execute permissions to the Domain Users group: 

        # setfacl -m group:"DOMAIN\Domain Users":r-x /srv/samba/example/

      3. Set permissions for the other ACL entry to deny access to users that do not match the other ACL entries: 

        # setfacl -R -m other::--- /srv/samba/example/

      These settings apply only to this directory. In Windows, these ACLs are mapped to the This folder only mode.

    3. To enable the permissions set in the previous step to be inherited by new file system objects created in this directory: 

      # setfacl -m default:group:"DOMAIN\Domain Admins":rwx /srv/samba/example/
# setfacl -m default:group:"DOMAIN\Domain Users":r-x /srv/samba/example/
# setfacl -m default:other::--- /srv/samba/example/

      With these settings, the This folder only mode for the principals is now set to This folder, subfolders, and files.

    Samba maps the permissions set in the procedure to the following Windows ACLs:

    PrincipalAccessApplies to

    Domain\Domain Admins

    Full control

    This folder, subfolders, and files

    Domain\Domain Users

    Read & execute

    This folder, subfolders, and files

    Everyone [a]

    None

    This folder, subfolders, and files

    owner (Unix User\owner) [b]

    Full control

    This folder only

    primary_group (Unix User\primary_group) [c]

    None

    This folder only

    CREATOR OWNER [d] [e]

    Full control

    Subfolders and files only

    CREATOR GROUP [e] [f]

    None

    Subfolders and files only

    [a] Samba maps the permissions for this principal from the other ACL entry.
    [b] Samba maps the owner of the directory to this entry.
    [c] Samba maps the primary group of the directory to this entry.
    [d] On new file system objects, the creator inherits automatically the permissions of this principal.
    [e] Configuring or removing these principals from the ACLs not supported on shares that use POSIX ACLs.
    [f] On new file system objects, the creator’s primary group inherits automatically the permissions of this principal.

1.8. Setting permissions on a share that uses POSIX ACLs

Optionally, to limit or grant access to a Samba share, you can set certain parameters in the share’s section in the /etc/samba/smb.conf file.

Note

Share-based permissions manage if a user, group, or host is able to access a share. These settings do not affect file system ACLs.

Use share-based settings to restrict access to shares, for example, to deny access from specific hosts.

Prerequisites

  • A share with POSIX ACLs has been set up.

1.8.1. Configuring user and group-based share access

User and group-based access control enables you to grant or deny access to a share for certain users and groups.

Prerequisites

  • The Samba share on which you want to set user or group-based access exists.

Procedure

  1. For example, to enable all members of the Domain Users group to access a share while access is denied for the user account, add the following parameters to the share’s configuration: 

    valid users = +DOMAIN\"Domain Users"
invalid users = DOMAIN\user

    The invalid users parameter has a higher priority than the valid users parameter. For example, if the user account is a member of the Domain Users group, access is denied to this account when you use the previous example.

  2. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

  • smb.conf(5) man page

1.8.2. Configuring host-based share access

Host-based access control enables you to grant or deny access to a share based on client’s host names, IP addresses, or IP range.

The following procedure explains how to enable the 127.0.0.1 IP address, the 192.0.2.0/24 IP range, and the client1.example.com host to access a share, and additionally deny access for the client2.example.com host:

Prerequisites

  • The Samba share on which you want to set host-based access exists.

Procedure

  1. Add the following parameters to the configuration of the share in the /etc/samba/smb.conf file: 

    hosts allow = 127.0.0.1 192.0.2.0/24 client1.example.com
hosts deny = client2.example.com

    The hosts deny parameter has a higher priority than hosts allow. For example, if client1.example.com resolves to an IP address that is listed in the hosts allow parameter, access for this host is denied.

  2. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

  • smb.conf(5) man page

1.9. Setting up a share that uses Windows ACLs

Samba supports setting Windows ACLs on shares and file system object. This enables you to:

  • Use the fine-granular Windows ACLs
  • Manage share permissions and file system ACLs using Windows

Alternatively, you can configure a share to use POSIX ACLs.

For details, see Setting up a Samba file share that uses POSIX ACLs.

Parts of this section were adopted from the Setting up a Share Using Windows ACLs documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

1.9.1. Granting the SeDiskOperatorPrivilege privilege

Only users and groups having the SeDiskOperatorPrivilege privilege granted can configure permissions on shares that use Windows ACLs.

Procedure

  1. For example, to grant the SeDiskOperatorPrivilege privilege to the DOMAIN\Domain Admins group: 

    # net rpc rights grant "DOMAIN\Domain Admins" SeDiskOperatorPrivilege -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
Successfully granted rights.
    Note

    In a domain environment, grant SeDiskOperatorPrivilege to a domain group. This enables you to centrally manage the privilege by updating a user’s group membership.

  2. To list all users and groups having SeDiskOperatorPrivilege granted: 

    # net rpc rights list privileges SeDiskOperatorPrivilege -U "DOMAIN\administrator"
Enter administrator's password:
SeDiskOperatorPrivilege:
  BUILTIN\Administrators
  DOMAIN\Domain Admins

1.9.2. Enabling Windows ACL support

To configure shares that support Windows ACLs, you must enable this feature in Samba.

Prerequisites

  • A user share is configured on the Samba server.

Procedure

  1. To enable it globally for all shares, add the following settings to the [global] section of the /etc/samba/smb.conf file: 

    vfs objects = acl_xattr
map acl inherit = yes
store dos attributes = yes

    Alternatively, you can enable Windows ACL support for individual shares, by adding the same parameters to a share’s section instead.

  2. Restart the smb service: 

    # systemctl restart smb

1.9.3. Adding a share that uses Windows ACLs

This section describes how to create a share named example, that shares the content of the /srv/samba/example/ directory, and uses Windows ACLs.

Procedure

  1. Create the folder if it does not exists. For example: 

    # mkdir -p /srv/samba/example/

  2. If you run SELinux in enforcing mode, set the samba_share_t context on the directory: 

    # semanage fcontext -a -t samba_share_t "/srv/samba/example(/.*)?"
# restorecon -Rv /srv/samba/example/

  3. Add the example share to the /etc/samba/smb.conf file. For example, to add the share write-enabled: 

    [example]
	path = /srv/samba/example/
	read only = no
    Note

    Regardless of the file system ACLs; if you do not set read only = no, Samba shares the directory in read-only mode.

  4. If you have not enabled Windows ACL support in the [global] section for all shares, add the following parameters to the [example] section to enable this feature for this share: 

    vfs objects = acl_xattr
map acl inherit = yes
store dos attributes = yes

  5. Verify the /etc/samba/smb.conf file: 

    # testparm

  6. Open the required ports and reload the firewall configuration using the firewall-cmd utility: 

    # firewall-cmd --permanent --add-service=samba
# firewall-cmd --reload

  7. Restart the smb service: 

    # systemctl restart smb

1.9.4. Managing share permissions and file system ACLs of a share that uses Windows ACLs

To manage share permissions and file system ACLs on a Samba share that uses Windows ACLs, use a Windows applications, such as Computer Management. For details, see the Windows documentation. Alternatively, use the smbcacls utility to manage ACLs.

Note

To modify the file system permissions from Windows, you must use an account that has the SeDiskOperatorPrivilege privilege granted.

Additional resources

1.10. Managing ACLs on an SMB share using smbcacls

The smbcacls utility can list, set, and delete ACLs of files and directories stored on an SMB share. You can use smbcacls to manage file system ACLs:

  • On a local or remote Samba server that uses advanced Windows ACLs or POSIX ACLs
  • On Red Hat Enterprise Linux to remotely manage ACLs on a share hosted on Windows

1.10.1. Access control entries

Each ACL entry of a file system object contains Access Control Entries (ACE) in the following format: 

security_principal:access_right/inheritance_information/permissions

Example 1.3. Access control entries

If the AD\Domain Users group has Modify permissions that apply to This folder, subfolders, and files on Windows, the ACL contains the following ACE: 

AD\Domain Users:ALLOWED/OI|CI/CHANGE

An ACE contains the following parts:

Security principal
The security principal is the user, group, or SID the permissions in the ACL are applied to.
Access right
Defines if access to an object is granted or denied. The value can be ALLOWED or DENIED.
Inheritance information

The following values exist:

Table 1.1. Inheritance settings

ValueDescriptionMaps to

OI

Object Inherit

This folder and files

CI

Container Inherit

This folder and subfolders

IO

Inherit Only

The ACE does not apply to the current file or directory

ID

Inherited

The ACE was inherited from the parent directory

Additionally, the values can be combined as follows:

Table 1.2. Inheritance settings combinations

Value combinationsMaps to the Windows Applies to setting

OI|CI

This folder, subfolders, and files

OI|CI|IO

Subfolders and files only

CI|IO

Subfolders only

OI|IO

Files only

Permissions

This value can be either a hex value that represents one or more Windows permissions or an smbcacls alias:

  • A hex value that represents one or more Windows permissions.

    The following table displays the advanced Windows permissions and their corresponding value in hex format:

    Table 1.3. Windows permissions and their corresponding smbcacls value in hex format

    Windows permissionsHex values

    Full control

    0x001F01FF

    Traverse folder / execute file

    0x00100020

    List folder / read data

    0x00100001

    Read attributes

    0x00100080

    Read extended attributes

    0x00100008

    Create files / write data

    0x00100002

    Create folders / append data

    0x00100004

    Write attributes

    0x00100100

    Write extended attributes

    0x00100010

    Delete subfolders and files

    0x00100040

    Delete

    0x00110000

    Read permissions

    0x00120000

    Change permissions

    0x00140000

    Take ownership

    0x00180000

    Multiple permissions can be combined as a single hex value using the bit-wise OR operation.

For details, see ACE mask calculation.

  • An smbcacls alias. The following table displays the available aliases:

    Table 1.4. Existing smbcacls aliases and their corresponding Windows permission

    smbcacls aliasMaps to Windows permission

    R

    Read

    READ

    Read & execute

    W

    Special:

    • Create files / write data
    • Create folders / append data
    • Write attributes
    • Write extended attributes
    • Read permissions

    D

    Delete

    P

    Change permissions

    O

    Take ownership

    X

    Traverse / execute

    CHANGE

    Modify

    FULL

    Full control

    Note

    You can combine single-letter aliases when you set permissions. For example, you can set RD to apply the Windows permission Read and Delete. However, you can neither combine multiple non-single-letter aliases nor combine aliases and hex values.

1.10.2. Displaying ACLs using smbcacls

To display ACLs on an SMB share, use the smbcacls utility. If you run smbcacls without any operation parameter, such as --add, the utility displays the ACLs of a file system object.

Procedure

For example, to list the ACLs of the root directory of the //server/example share: 

# smbcacls //server/example / -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
REVISION:1
CONTROL:SR|PD|DI|DP
OWNER:AD\Administrators
GROUP:AD\Domain Users
ACL:AD\Administrator:ALLOWED/OI|CI/FULL
ACL:AD\Domain Users:ALLOWED/OI|CI/CHANGE
ACL:AD\Domain Guests:ALLOWED/OI|CI/0x00100021

The output of the command displays:

  • REVISION: The internal Windows NT ACL revision of the security descriptor
  • CONTROL: Security descriptor control
  • OWNER: Name or SID of the security descriptor’s owner
  • GROUP: Name or SID of the security descriptor’s group
  • ACL entries. For details, see Access control entries.

1.10.3. ACE mask calculation

In most situations, when you add or update an ACE, you use the smbcacls aliases listed in Existing smbcacls aliases and their corresponding Windows permission.

However, if you want to set advanced Windows permissions as listed in Windows permissions and their corresponding smbcacls value in hex format, you must use the bit-wise OR operation to calculate the correct value. You can use the following shell command to calculate the value: 

# echo $(printf '0x%X' $(( hex_value_1 | hex_value_2 | ... )))

Example 1.4. Calculating an ACE Mask

You want to set the following permissions:

  • Traverse folder / execute file (0x00100020)
  • List folder / read data (0x00100001)
  • Read attributes (0x00100080)

To calculate the hex value for the previous permissions, enter: 

# echo $(printf '0x%X' $(( 0x00100020 | 0x00100001 | 0x00100080 )))
0x1000A1

Use the returned value when you set or update an ACE.

1.10.4. Adding, updating, and removing an ACL using smbcacls

Depending on the parameter you pass to the smbcacls utility, you can add, update, and remove ACLs from a file or directory.

Adding an ACL

To add an ACL to the root of the //server/example share that grants CHANGE permissions for This folder, subfolders, and files to the AD\Domain Users group: 

# smbcacls //server/example / -U "DOMAIN\administrator --add ACL:"AD\Domain Users":ALLOWED/OI|CI/CHANGE
Updating an ACL

Updating an ACL is similar to adding a new ACL. You update an ACL by overriding the ACL using the --modify parameter with an existing security principal. If smbcacls finds the security principal in the ACL list, the utility updates the permissions. Otherwise the command fails with an error: 

ACL for SID principal_name not found

For example, to update the permissions of the AD\Domain Users group and set them to READ for This folder, subfolders, and files: 

# smbcacls //server/example / -U "DOMAIN\administrator --modify ACL:"AD\Domain Users":ALLOWED/OI|CI/READ
Deleting an ACL

To delete an ACL, pass the --delete parameter with the exact ACL to the smbcacls utility. For example: 

# smbcacls //server/example / -U "DOMAIN\administrator --delete ACL:"AD\Domain Users":ALLOWED/OI|CI/READ

1.11. Enabling users to share directories on a Samba server

On a Samba server, you can configure that users can share directories without root permissions.

1.11.1. Enabling the user shares feature

Before users can share directories, the administrator must enable user shares in Samba.

For example, to enable only members of the local example group to create user shares.

Procedure

  1. Create the local example group, if it does not exist: 

    # groupadd example

  2. Prepare the directory for Samba to store the user share definitions and set its permissions properly. For example:

    1. Create the directory: 

      # mkdir -p /var/lib/samba/usershares/

    2. Set write permissions for the example group: 

      # chgrp example /var/lib/samba/usershares/
# chmod 1770 /var/lib/samba/usershares/
    3. Set the sticky bit to prevent users to rename or delete files stored by other users in this directory.

  3. Edit the /etc/samba/smb.conf file and add the following to the [global] section:

    1. Set the path to the directory you configured to store the user share definitions. For example: 

      usershare path = /var/lib/samba/usershares/

    2. Set how many user shares Samba allows to be created on this server. For example: 

      usershare max shares = 100

      If you use the default of 0 for the usershare max shares parameter, user shares are disabled.

    3. Optionally, set a list of absolute directory paths. For example, to configure that Samba only allows to share subdirectories of the /data and /srv directory to be shared, set: 

      usershare prefix allow list = /data /srv

    For a list of further user share-related parameters you can set, see the USERSHARES section in the smb.conf(5) man page.

  4. Verify the /etc/samba/smb.conf file: 

    # testparm

  5. Reload the Samba configuration: 

    # smbcontrol all reload-config

    Users are now able to create user shares.

1.11.2. Adding a user share

After you enabled the user share feature in Samba, users can share directories on the Samba server without root permissions by running the net usershare add command.

Synopsis of the net usershare add command:

net usershare add share_name path [[ comment ] | [ ACLs ]] [ guest_ok=y|n ]

Important

If you set ACLs when you create a user share, you must specify the comment parameter prior to the ACLs. To set an empty comment, use an empty string in double quotes.

Note that users can only enable guest access on a user share, if the administrator set usershare allow guests = yes in the [global] section in the /etc/samba/smb.conf file.

Example 1.5. Adding a user share

A user wants to share the /srv/samba/ directory on a Samba server. The share should be named example, have no comment set, and should be accessible by guest users. Additionally, the share permissions should be set to full access for the AD\Domain Users group and read permissions for other users. To add this share, run as the user: 

$ net usershare add example /srv/samba/ "" "AD\Domain Users":F,Everyone:R guest_ok=yes

1.11.3. Updating settings of a user share

To update settings of a user share, override the share by using the net usershare add command with the same share name and the new settings.

See Adding a user share.

1.11.4. Displaying information about existing user shares

Users can enter the net usershare info command on a Samba server to display user shares and their settings.

Prerequisites

  • A user share is configured on the Samba server.

Procedure

  1. To display all user shares created by any user: 

    $ net usershare info -l
[share_1]
path=/srv/samba/
comment=
usershare_acl=Everyone:R,host_name\user:F,
guest_ok=y
...

    To list only shares created by the user who runs the command, omit the -l parameter.

  2. To display only the information about specific shares, pass the share name or wild cards to the command. For example, to display the information about shares whose name starts with share_: 

    $ net usershare info -l share_*

1.11.5. Listing user shares

If you want to list only the available user shares without their settings on a Samba server, use the net usershare list command.

Prerequisites

  • A user share is configured on the Samba server.

Procedure

  1. To list the shares created by any user: 

    $ net usershare list -l
share_1
share_2
...

    To list only shares created by the user who runs the command, omit the -l parameter.

  2. To list only specific shares, pass the share name or wild cards to the command. For example, to list only shares whose name starts with share_: 

    $ net usershare list -l share_*

1.11.6. Deleting a user share

To delete a user share, use the command net usershare delete command as the user who created the share or as the root user.

Prerequisites

  • A user share is configured on the Samba server.

Procedure

$ net usershare delete share_name

1.12. Configuring a share to allow access without authentication

In certain situations, you want to share a directory to which users can connect without authentication. To configure this, enable guest access on a share.

Warning

Shares that do not require authentication can be a security risk.

1.12.1. Enabling guest access to a share

If guest access is enabled on a share, Samba maps guest connections to the operating system account set in the guest account parameter. Guest users can access files on this share if at least one of the following conditions is satisfied:

  • The account is listed in file system ACLs
  • The POSIX permissions for other users allow it

Example 1.6. Guest share permissions

If you configured Samba to map the guest account to nobody, which is the default, the ACLs in the following example:

  • Allow guest users to read file1.txt
  • Allow guest users to read and modify file2.txt
  • Prevent guest users to read or modify file3.txt 
-rw-r--r--. 1 root       root      1024 1. Sep 10:00 file1.txt
-rw-r-----. 1 nobody     root      1024 1. Sep 10:00 file2.txt
-rw-r-----. 1 root       root      1024 1. Sep 10:00 file3.txt

Procedure

  1. Edit the /etc/samba/smb.conf file:

    1. If this is the first guest share you set up on this server:

      1. Set map to guest = Bad User in the [global] section: 

        [global]
        ...
        map to guest = Bad User

        With this setting, Samba rejects login attempts that use an incorrect password unless the user name does not exist. If the specified user name does not exist and guest access is enabled on a share, Samba treats the connection as a guest log in.

      2. By default, Samba maps the guest account to the nobody account on Red Hat Enterprise Linux. Alternatively, you can set a different account. For example: 

        [global]
        ...
        guest account = user_name

        The account set in this parameter must exist locally on the Samba server. For security reasons, Red Hat recommends using an account that does not have a valid shell assigned.

    2. Add the guest ok = yes setting to the [example] share section: 

      [example]
        ...
        guest ok = yes

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Reload the Samba configuration: 

    # smbcontrol all reload-config

1.13. Configuring Samba for macOS clients

The fruit virtual file system (VFS) Samba module provides enhanced compatibility with Apple server message block (SMB) clients.

1.13.1. Optimizing the Samba configuration for providing file shares for macOS clients

This section describes how to configure the fruit module for all Samba shares hosted on the server to optimize Samba file shares for macOS clients.

Note

Red Hat recommends enabling the fruit module globally. Clients using macOS negotiate the server server message block version 2 (SMB2) Apple (AAPL) protocol extensions when the client establishes the first connection to the server. If the client first connects to a share without AAPL extensions enabled, the client does not use the extensions for any share of the server.

Prerequisites

  • Samba is configured as a file server.

Procedure

  1. Edit the /etc/samba/smb.conf file, and enable the fruit and streams_xattr VFS modules in the [global] section: 

    vfs objects = fruit streams_xattr
    Important

    You must enable the fruit module before enabling streams_xattr. The fruit module uses alternate data streams (ADS). For this reason, you must also enable the streams_xattr module.

  2. Optionally, to provide macOS Time Machine support on a share, add the following setting to the share configuration in the /etc/samba/smb.conf file: 

    fruit:time machine = yes

  3. Verify the /etc/samba/smb.conf file: 

    # testparm

  4. Reload the Samba configuration: 

    # smbcontrol all reload-config

Additional resources

1.14. Using the smbclient utility to access an SMB share

The smbclient utility enables you to access file shares on an SMB server, similarly to a command-line FTP client. You can use it, for example, to upload and download files to and from a share.

Prerequisites

  • The samba-client package is installed.

1.14.1. How the smbclient interactive mode works

For example, to authenticate to the example share hosted on server using the DOMAIN\user account: 

# smbclient -U "DOMAIN\user" //server/example
Enter domain\user's password:
Try "help" to get a list of possible commands.
smb: \>

After smbclient connected successfully to the share, the utility enters the interactive mode and shows the following prompt: 

smb: \>

To display all available commands in the interactive shell, enter: 

smb: \> help

To display the help for a specific command, enter: 

smb: \> help command_name

Additional resources

  • smbclient(1) man page

1.14.2. Using smbclient in interactive mode

If you use smbclient without the -c parameter, the utility enters the interactive mode. The following procedure shows how to connect to an SMB share and download a file from a subdirectory.

Procedure

  1. Connect to the share: 

    # smbclient -U "DOMAIN\user_name" //server_name/share_name

  2. Change into the /example/ directory: 

    smb: \> d /example/

  3. List the files in the directory: 

    smb: \example\> ls
  .                    D         0  Thu Nov 1 10:00:00 2018
  ..                   D         0  Thu Nov 1 10:00:00 2018
  example.txt          N   1048576  Thu Nov 1 10:00:00 2018

         9950208 blocks of size 1024. 8247144 blocks available

  4. Download the example.txt file: 

    smb: \example\> get example.txt
getting file \directory\subdirectory\example.txt of size 1048576 as example.txt (511975,0 KiloBytes/sec) (average 170666,7 KiloBytes/sec)

  5. Disconnect from the share: 

    smb: \example\> exit

1.14.3. Using smbclient in scripting mode

If you pass the -c parameter to smbclient, you can automatically execute the commands on the remote SMB share. This enables you to use smbclient in scripts.

The following procedure shows how to connect to an SMB share and download a file from a subdirectory.

Procedure

  • Use the following command to connect to the share, change into the example directory, download the example.txt file: 
# smbclient -U DOMAIN\user_name //server_name/share_name -c "cd /example/ ; get example.txt ; exit"

1.15. Setting up Samba as a print server

If you set up Samba as a print server, clients in your network can use Samba to print. Additionally, Windows clients can, if configured, download the driver from the Samba server.

Parts of this section were adopted from the Setting up Samba as a Print Server documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

Prerequisites

Samba has been set up in one of the following modes:

1.15.1. Enabling print server support in Samba

By default, print server support is not enabled in Samba. To use Samba as a print server, you must configure Samba accordingly.

Note

Print jobs and printer operations require remote procedure calls (RPCs). By default, Samba starts the rpcd_spoolss service on demand to manage RPCs. During the first RPC call, or when you update the printer list in CUPS, Samba retrieves the printer information from CUPS. This can require approximately 1 second per printer. Therefore, if you have more than 50 printers, tune the rpcd_spoolss settings.

Prerequisites

  • The printers are configured in a CUPS server.

    For details about configuring printers in CUPS, see the documentation provided in the CUPS web console (https://printserver:631/help) on the print server.

Procedure

  1. Edit the /etc/samba/smb.conf file:

    1. Add the [printers] section to enable the printing backend in Samba: 

      [printers]
        comment = All Printers
        path = /var/tmp/
        printable = yes
        create mask = 0600
      Important

      The [printers] share name is hard-coded and cannot be changed.

    2. If the CUPS server runs on a different host or port, specify the setting in the [printers] section: 

      cups server = printserver.example.com:631

    3. If you have many printers, set the number of idle seconds to a higher value than the numbers of printers connected to CUPS. For example, if you have 100 printers, set in the [global] section: 

      rpcd_spoolss:idle_seconds = 200

      If this setting does not scale in your environment, also increase the number of rpcd_spoolss workers in the [global] section: 

      rpcd_spoolss:num_workers = 10

      By default, rpcd_spoolss starts 5 workers.

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Open the required ports and reload the firewall configuration using the firewall-cmd utility: 

    # firewall-cmd --permanent --add-service=samba
# firewall-cmd --reload

  4. Restart the smb service: 

    # systemctl restart smb

    After restarting the service, Samba automatically shares all printers that are configured in the CUPS back end. If you want to manually share only specific printers, see Manually sharing specific printers.

Verification

  • Submit a print job. For example, to print a PDF file, enter: 

    # smbclient -Uuser //sambaserver.example.com/printer_name -c "print example.pdf"

1.15.2. Manually sharing specific printers

If you configured Samba as a print server, by default, Samba shares all printers that are configured in the CUPS back end. The following procedure explains how to share only specific printers.

Prerequisites

  • Samba is set up as a print server

Procedure

  1. Edit the /etc/samba/smb.conf file:

    1. In the [global] section, disable automatic printer sharing by setting: 

      load printers = no

    2. Add a section for each printer you want to share. For example, to share the printer named example in the CUPS back end as Example-Printer in Samba, add the following section: 

      [Example-Printer]
        path = /var/tmp/
        printable = yes
        printer name = example

      You do not need individual spool directories for each printer. You can set the same spool directory in the path parameter for the printer as you set in the [printers] section.

  2. Verify the /etc/samba/smb.conf file: 

    # testparm

  3. Reload the Samba configuration: 

    # smbcontrol all reload-config

1.16. Setting up automatic printer driver downloads for Windows clients on Samba print servers

If you are running a Samba print server for Windows clients, you can upload drivers and preconfigure printers. If a user connects to a printer, Windows automatically downloads and installs the driver locally on the client. The user does not require local administrator permissions for the installation. Additionally, Windows applies preconfigured driver settings, such as the number of trays.

Parts of this section were adopted from the Setting up Automatic Printer Driver Downloads for Windows Clients documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

Prerequisites

  • Samba is set up as a print server

1.16.1. Basic information about printer drivers

This section provides general information about printer drivers.

Supported driver model version

Samba only supports the printer driver model version 3 which is supported in Windows 2000 and later, and Windows Server 2000 and later. Samba does not support the driver model version 4, introduced in Windows 8 and Windows Server 2012. However, these and later Windows versions also support version 3 drivers.

Package-aware drivers

Samba does not support package-aware drivers.

Preparing a printer driver for being uploaded

Before you can upload a driver to a Samba print server:

  • Unpack the driver if it is provided in a compressed format.

  • Some drivers require to start a setup application that installs the driver locally on a Windows host. In certain situations, the installer extracts the individual files into the operating system’s temporary folder during the setup runs. To use the driver files for uploading:

    1. Start the installer.
    2. Copy the files from the temporary folder to a new location.
    3. Cancel the installation.

Ask your printer manufacturer for drivers that support uploading to a print server.

Providing 32-bit and 64-bit drivers for a printer to a client

To provide the driver for a printer for both 32-bit and 64-bit Windows clients, you must upload a driver with exactly the same name for both architectures. For example, if you are uploading the 32-bit driver named Example PostScript and the 64-bit driver named Example PostScript (v1.0), the names do not match. Consequently, you can only assign one of the drivers to a printer and the driver will not be available for both architectures.

1.16.2. Enabling users to upload and preconfigure drivers

To be able to upload and preconfigure printer drivers, a user or a group needs to have the SePrintOperatorPrivilege privilege granted. A user must be added into the printadmin group. Red Hat Enterprise Linux automatically creates this group when you install the samba package. The printadmin group gets assigned the lowest available dynamic system GID that is lower than 1000.

Procedure

  1. For example, to grant the SePrintOperatorPrivilege privilege to the printadmin group: 

    # net rpc rights grant "printadmin" SePrintOperatorPrivilege -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
Successfully granted rights.
    Note

    In a domain environment, grant SePrintOperatorPrivilege to a domain group. This enables you to centrally manage the privilege by updating a user’s group membership.

  2. To list all users and groups having SePrintOperatorPrivilege granted: 

    # net rpc rights list privileges SePrintOperatorPrivilege -U "DOMAIN\administrator"
Enter administrator's password:
SePrintOperatorPrivilege:
  BUILTIN\Administrators
  DOMAIN\printadmin

1.16.3. Setting up the print$ share

Windows operating systems download printer drivers from a share named print$ from a print server. This share name is hard-coded in Windows and cannot be changed.

The following procedure explains how to share the /var/lib/samba/drivers/ directory as print$, and enable members of the local printadmin group to upload printer drivers.

Procedure

  1. Add the [print$] section to the /etc/samba/smb.conf file: 

    [print$]
        path = /var/lib/samba/drivers/
        read only = no
        write list = @printadmin
        force group = @printadmin
        create mask = 0664
        directory mask = 2775

    Using these settings:

    • Only members of the printadmin group can upload printer drivers to the share.
    • The group of new created files and directories will be set to printadmin.
    • The permissions of new files will be set to 664.
    • The permissions of new directories will be set to 2775.

  2. To upload only 64-bit drivers for all printers, include this setting in the [global] section in the /etc/samba/smb.conf file: 

    spoolss: architecture = Windows x64

    Without this setting, Windows only displays drivers for which you have uploaded at least the 32-bit version.

  3. Verify the /etc/samba/smb.conf file: 

    # testparm

  4. Reload the Samba configuration 

    # smbcontrol all reload-config

  5. Create the printadmin group if it does not exists: 

    # groupadd printadmin

  6. Grant the SePrintOperatorPrivilege privilege to the printadmin group. 

    # net rpc rights grant "printadmin" SePrintOperatorPrivilege -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
Successfully granted rights.

  7. If you run SELinux in enforcing mode, set the samba_share_t context on the directory: 

    # semanage fcontext -a -t samba_share_t "/var/lib/samba/drivers(/.)?" # *restorecon -Rv /var/lib/samba/drivers/

  8. Set the permissions on the /var/lib/samba/drivers/ directory:

    • If you use POSIX ACLs, set: 

      # chgrp -R "printadmin" /var/lib/samba/drivers/
# chmod -R 2775 /var/lib/samba/drivers/

    • If you use Windows ACLs, set:

      PrincipalAccessApply to

      CREATOR OWNER

      Full control

      Subfolders and files only

      Authenticated Users

      Read & execute, List folder contents, Read

      This folder, subfolders, and files

      printadmin

      Full control

      This folder, subfolders, and files

      For details about setting ACLs on Windows, see the Windows documentation.

Additional resources

1.16.4. Creating a GPO to enable clients to trust the Samba print server

For security reasons, recent Windows operating systems prevent clients from downloading non-package-aware printer drivers from an untrusted server. If your print server is a member in an AD, you can create a Group Policy Object (GPO) in your domain to trust the Samba server.

Prerequisites

  • The Samba print server is a member of an AD domain.
  • The Windows computer you are using to create the GPO must have the Windows Remote Server Administration Tools (RSAT) installed. For details, see the Windows documentation.

Procedure

  1. Log into a Windows computer using an account that is allowed to edit group policies, such as the AD domain Administrator user.
  2. Open the Group Policy Management Console.

  3. Right-click to your AD domain and select Create a GPO in this domain, and Link it here.

    samba create new GPO
  4. Enter a name for the GPO, such as Legacy Printer Driver Policy and click OK. The new GPO will be displayed under the domain entry.
  5. Right-click to the newly-created GPO and select Edit to open the Group Policy Management Editor.

  6. Navigate to Computer Configuration → Policies → Administrative Templates → Printers.

    samba select printer GPO group

  7. On the right side of the window, double-click Point and Print Restriction to edit the policy:

    1. Enable the policy and set the following options:

      1. Select Users can only point and print to these servers and enter the fully-qualified domain name (FQDN) of the Samba print server to the field next to this option.

      2. In both check boxes under Security Prompts, select Do not show warning or elevation prompt.

        samba GPO point and print
    2. Click OK.

  8. Double-click Package Point and Print - Approved servers to edit the policy:

    1. Enable the policy and click the Show button.

    2. Enter the FQDN of the Samba print server.

      samba GPO approved servers
    3. Close both the Show Contents and the policy’s properties window by clicking OK.
  9. Close the Group Policy Management Editor.
  10. Close the Group Policy Management Console.

After the Windows domain members applied the group policy, printer drivers are automatically downloaded from the Samba server when a user connects to a printer.

Additional resources

  • For using group policies, see the Windows documentation.

1.16.5. Uploading drivers and preconfiguring printers

Use the Print Management application on a Windows client to upload drivers and preconfigure printers hosted on the Samba print server. For further details, see the Windows documentation.

1.17. Running Samba on a server with FIPS mode enabled

This section provides an overview of the limitations of running Samba with FIPS mode enabled. It also provides the procedure for enabling FIPS mode on a Red Hat Enterprise Linux host running Samba.

1.17.1. Limitations of using Samba in FIPS mode

The following Samba modes and features work in FIPS mode under the indicated conditions:

  • Samba as a domain member only in Active Directory (AD) or Red Hat Identity Management (IdM) environments with Kerberos authentication that uses AES ciphers.
  • Samba as a file server on an Active Directory domain member. However, this requires that clients use Kerberos to authenticate to the server.

Due to the increased security of FIPS, the following Samba features and modes do not work if FIPS mode is enabled:

  • NT LAN Manager (NTLM) authentication because RC4 ciphers are blocked
  • The server message block version 1 (SMB1) protocol
  • The stand-alone file server mode because it uses NTLM authentication
  • NT4-style domain controllers
  • NT4-style domain members. Note that Red Hat continues supporting the primary domain controller (PDC) functionality IdM uses in the background.
  • Password changes against the Samba server. You can only perform password changes using Kerberos against an Active Directory domain controller.

The following feature is not tested in FIPS mode and, therefore, is not supported by Red Hat:

  • Running Samba as a print server

1.17.2. Using Samba in FIPS mode

This section describes how to enable the FIPS mode on a RHEL host that runs Samba.

Prerequisites

  • Samba is configured on the Red Hat Enterprise Linux host.
  • Samba runs in a mode that is supported in FIPS mode.

Procedure

  1. Enable the FIPS mode on RHEL: 

    # fips-mode-setup --enable

  2. Reboot the server: 

    # reboot

  3. Use the testparm utility to verify the configuration: 

    # testparm -s

    If the command displays any errors or incompatibilities, fix them to ensure that Samba works correctly.

Additional resources

1.18. Tuning the performance of a Samba server

Learn what settings can improve the performance of Samba in certain situations, and which settings can have a negative performance impact.

Parts of this section were adopted from the Performance Tuning documentation published in the Samba Wiki. License: CC BY 4.0. Authors and contributors: See the history tab on the Wiki page.

Prerequisites

  • Samba is set up as a file or print server

1.18.1. Setting the SMB protocol version

Each new SMB version adds features and improves the performance of the protocol. The recent Windows and Windows Server operating systems always supports the latest protocol version. If Samba also uses the latest protocol version, Windows clients connecting to Samba benefit from the performance improvements. In Samba, the default value of the server max protocol is set to the latest supported stable SMB protocol version.

Note

To always have the latest stable SMB protocol version enabled, do not set the server max protocol parameter. If you set the parameter manually, you will need to modify the setting with each new version of the SMB protocol, to have the latest protocol version enabled.

The following procedure explains how to use the default value in the server max protocol parameter.

Procedure

  1. Remove the server max protocol parameter from the [global] section in the /etc/samba/smb.conf file.

  2. Reload the Samba configuration 

    # smbcontrol all reload-config

1.18.2. Tuning shares with directories that contain a large number of files

Linux supports case-sensitive file names. For this reason, Samba needs to scan directories for uppercase and lowercase file names when searching or accessing a file. You can configure a share to create new files only in lowercase or uppercase, which improves the performance.

Prerequisites

  • Samba is configured as a file server

Procedure

  1. Rename all files on the share to lowercase.

    Note

    Using the settings in this procedure, files with names other than in lowercase will no longer be displayed.

  2. Set the following parameters in the share’s section: 

    case sensitive = true
default case = lower
preserve case = no
short preserve case = no

    For details about the parameters, see their descriptions in the smb.conf(5) man page.

  3. Verify the /etc/samba/smb.conf file: 

    # testparm

  4. Reload the Samba configuration: 

    # smbcontrol all reload-config

After you applied these settings, the names of all newly created files on this share use lowercase. Because of these settings, Samba no longer needs to scan the directory for uppercase and lowercase, which improves the performance.

1.18.3. Settings that can have a negative performance impact

By default, the kernel in Red Hat Enterprise Linux is tuned for high network performance. For example, the kernel uses an auto-tuning mechanism for buffer sizes. Setting the socket options parameter in the /etc/samba/smb.conf file overrides these kernel settings. As a result, setting this parameter decreases the Samba network performance in most cases.

To use the optimized settings from the Kernel, remove the socket options parameter from the [global] section in the /etc/samba/smb.conf.

1.19. Configuring Samba to be compatible with clients that require an SMB version lower than the default

Samba uses a reasonable and secure default value for the minimum server message block (SMB) version it supports. However, if you have clients that require an older SMB version, you can configure Samba to support it.

1.19.1. Setting the minimum SMB protocol version supported by a Samba server

In Samba, the server min protocol parameter in the /etc/samba/smb.conf file defines the minimum server message block (SMB) protocol version the Samba server supports. This section describes how to change the minimum SMB protocol version.

Note

By default, Samba on RHEL 8.2 and later supports only SMB2 and newer protocol versions. Red Hat recommends to not use the deprecated SMB1 protocol. However, if your environment requires SMB1, you can manually set the server min protocol parameter to NT1 to re-enable SMB1.

Prerequisites

  • Samba is installed and configured.

Procedure

  1. Edit the /etc/samba/smb.conf file, add the server min protocol parameter, and set the parameter to the minimum SMB protocol version the server should support. For example, to set the minimum SMB protocol version to SMB3, add: 

    server min protocol = SMB3

  2. Restart the smb service: 

    # systemctl restart smb

Additional resources

  • smb.conf(5) man page

1.20. Frequently used Samba command-line utilities

This chapter describes frequently used commands when working with a Samba server.

1.20.1. Using the net ads join and net rpc join commands

Using the join subcommand of the net utility, you can join Samba to an AD or NT4 domain. To join the domain, you must create the /etc/samba/smb.conf file manually, and optionally update additional configurations, such as PAM.

Important

Red Hat recommends using the realm utility to join a domain. The realm utility automatically updates all involved configuration files.

Procedure

  1. Manually create the /etc/samba/smb.conf file with the following settings:

    • For an AD domain member: 

      [global]
workgroup = domain_name
security = ads
passdb backend = tdbsam
realm = AD_REALM

    • For an NT4 domain member: 

      [global]
workgroup = domain_name
security = user
passdb backend = tdbsam
  2. Add an ID mapping configuration for the * default domain and for the domain you want to join to the [global] section in the /etc/samba/smb.conf file.

  3. Verify the /etc/samba/smb.conf file: 

    # testparm

  4. Join the domain as the domain administrator:

    • To join an AD domain: 

      # net ads join -U "DOMAIN\administrator"

    • To join an NT4 domain: 

      # net rpc join -U "DOMAIN\administrator"

  5. Append the winbind source to the passwd and group database entry in the /etc/nsswitch.conf file: 

    passwd:     files winbind
group:      files winbind

  6. Enable and start the winbind service: 

    # systemctl enable --now winbind

  7. Optionally, configure PAM using the authselect utility.

    For details, see the authselect(8) man page.

  8. Optionally for AD environments, configure the Kerberos client.

    For details, see the documentation of your Kerberos client.

Additional resources

1.20.2. Using the net rpc rights command

In Windows, you can assign privileges to accounts and groups to perform special operations, such as setting ACLs on a share or upload printer drivers. On a Samba server, you can use the net rpc rights command to manage privileges.

Listing privileges you can set

To list all available privileges and their owners, use the net rpc rights list command. For example: 

# net rpc rights list -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
     SeMachineAccountPrivilege  Add machines to domain
      SeTakeOwnershipPrivilege  Take ownership of files or other objects
             SeBackupPrivilege  Back up files and directories
            SeRestorePrivilege  Restore files and directories
     SeRemoteShutdownPrivilege  Force shutdown from a remote system
      SePrintOperatorPrivilege  Manage printers
           SeAddUsersPrivilege  Add users and groups to the domain
       SeDiskOperatorPrivilege  Manage disk shares
           SeSecurityPrivilege  System security
Granting privileges

To grant a privilege to an account or group, use the net rpc rights grant command.

For example, grant the SePrintOperatorPrivilege privilege to the DOMAIN\printadmin group: 

# net rpc rights grant "DOMAIN\printadmin" SePrintOperatorPrivilege -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
Successfully granted rights.
Revoking privileges

To revoke a privilege from an account or group, use the net rpc rights revoke command.

For example, to revoke the SePrintOperatorPrivilege privilege from the DOMAIN\printadmin group: 

# net rpc rights remoke "DOMAIN\printadmin" SePrintOperatorPrivilege -U "DOMAIN\administrator"
Enter DOMAIN\administrator's password:
Successfully revoked rights.

1.20.3. Using the net rpc share command

The net rpc share command provides the capability to list, add, and remove shares on a local or remote Samba or Windows server.

Listing shares

To list the shares on an SMB server, use the net rpc share list command. Optionally, pass the -S server_name parameter to the command to list the shares of a remote server. For example: 

# net rpc share list -U "DOMAIN\administrator" -S server_name
Enter DOMAIN\administrator's password:
IPC$
share_1
share_2
...
Note

Shares hosted on a Samba server that have browseable = no set in their section in the /etc/samba/smb.conf file are not displayed in the output.

Adding a share

The net rpc share add command enables you to add a share to an SMB server.

For example, to add a share named example on a remote Windows server that shares the C:\example\ directory: 

# net rpc share add example="C:\example" -U "DOMAIN\administrator" -S server_name
Note

You must omit the trailing backslash in the path when specifying a Windows directory name.

To use the command to add a share to a Samba server:

  • The user specified in the -U parameter must have the SeDiskOperatorPrivilege privilege granted on the destination server.
  • You must write a script that adds a share section to the /etc/samba/smb.conf file and reloads Samba. The script must be set in the add share command parameter in the [global] section in /etc/samba/smb.conf. For further details, see the add share command description in the smb.conf(5) man page.
Removing a share

The net rpc share delete command enables you to remove a share from an SMB server.

For example, to remove the share named example from a remote Windows server: 

# net rpc share delete example -U "DOMAIN\administrator" -S server_name

To use the command to remove a share from a Samba server:

  • The user specified in the -U parameter must have the SeDiskOperatorPrivilege privilege granted.
  • You must write a script that removes the share’s section from the /etc/samba/smb.conf file and reloads Samba. The script must be set in the delete share command parameter in the [global] section in /etc/samba/smb.conf. For further details, see the delete share command description in the smb.conf(5) man page.

1.20.4. Using the net user command

The net user command enables you to perform the following actions on an AD DC or NT4 PDC:

  • List all user accounts
  • Add users
  • Remove Users
Note

Specifying a connection method, such as ads for AD domains or rpc for NT4 domains, is only required when you list domain user accounts. Other user-related subcommands can auto-detect the connection method.

Pass the -U user_name parameter to the command to specify a user that is allowed to perform the requested action.

Listing domain user accounts

To list all users in an AD domain: 

# net ads user -U "DOMAIN\administrator"

To list all users in an NT4 domain: 

# net rpc user -U "DOMAIN\administrator"
Adding a user account to the domain

On a Samba domain member, you can use the net user add command to add a user account to the domain.

For example, add the user account to the domain:

  1. Add the account: 

    # net user add user password -U "DOMAIN\administrator"
User user added

  2. Optionally, use the remote procedure call (RPC) shell to enable the account on the AD DC or NT4 PDC. For example: 

    # net rpc shell -U DOMAIN\administrator -S DC_or_PDC_name
Talking to domain DOMAIN (S-1-5-21-1424831554-512457234-5642315751)

net rpc> user edit disabled user: no
Set user's disabled flag from [yes] to [no]

net rpc> exit
Deleting a user account from the domain

On a Samba domain member, you can use the net user delete command to remove a user account from the domain.

For example, to remove the user account from the domain: 

# net user delete user -U "DOMAIN\administrator"
User user deleted

1.20.5. Using the rpcclient utility

The rpcclient utility enables you to manually execute client-side Microsoft Remote Procedure Call (MS-RPC) functions on a local or remote SMB server. However, most of the features are integrated into separate utilities provided by Samba. Use rpcclient only for testing MS-PRC functions.

Prerequisites

  • The samba-client package is installed.
Examples

For example, you can use the rpcclient utility to:

  • Manage the printer Spool Subsystem (SPOOLSS).

    Example 1.7. Assigning a Driver to a Printer

    # rpcclient server_name -U "DOMAIN\administrator" -c 'setdriver "printer_name" "driver_name"'
Enter DOMAIN\administrators password:
Successfully set printer_name to driver driver_name.

  • Retrieve information about an SMB server.

    Example 1.8. Listing all File Shares and Shared Printers

    # rpcclient server_name -U "DOMAIN\administrator" -c 'netshareenum'
Enter DOMAIN\administrators password:
netname: Example_Share
	remark:
	path:   C:\srv\samba\example_share\
	password:
netname: Example_Printer
	remark:
	path:   C:\var\spool\samba\
	password:

  • Perform actions using the Security Account Manager Remote (SAMR) protocol.

    Example 1.9. Listing Users on an SMB Server

    # rpcclient server_name -U "DOMAIN\administrator" -c 'enumdomusers'
Enter DOMAIN\administrators password:
user:[user1] rid:[0x3e8]
user:[user2] rid:[0x3e9]

    If you run the command against a standalone server or a domain member, it lists the users in the local database. Running the command against an AD DC or NT4 PDC lists the domain users.

Additional resources

  • rpcclient(1) man page

1.20.6. Using the samba-regedit application

Certain settings, such as printer configurations, are stored in the registry on the Samba server. You can use the ncurses-based samba-regedit application to edit the registry of a Samba server.

samba regedit

Prerequisites

  • The samba-client package is installed.

Procedure

To start the application, enter: 

# samba-regedit

Use the following keys:

  • Cursor up and cursor down: Navigate through the registry tree and the values.
  • Enter: Opens a key or edits a value.
  • Tab: Switches between the Key and Value pane.
  • Ctrl+C: Closes the application.

1.20.7. Using the smbcontrol utility

The smbcontrol utility enables you to send command messages to the smbd, nmbd, winbindd, or all of these services. These control messages instruct the service, for example, to reload its configuration.

The procedure in this section shows how to to reload the configuration of the smbd, nmbd, winbindd services by sending the reload-config message type to the all destination.

Prerequisites

  • The samba-common-tools package is installed.

Procedure

# smbcontrol all reload-config

Additional resources

  • smbcontrol(1) man page

1.20.8. Using the smbpasswd utility

The smbpasswd utility manages user accounts and passwords in the local Samba database.

Prerequisites

  • The samba-common-tools package is installed.

Procedure

  1. If you run the command as a user, smbpasswd changes the Samba password of the user who run the command. For example: 

    [user@server ~]$ smbpasswd
New SMB password: password
Retype new SMB password: password

  2. If you run smbpasswd as the root user, you can use the utility, for example, to:

    • Create a new user: 

      [root@server ~]# smbpasswd -a user_name
New SMB password: password
Retype new SMB password: password
Added user user_name.
      Note

      Before you can add a user to the Samba database, you must create the account in the local operating system. See the Adding a new user from the command line section in the Configuring basic system settings guide.

    • Enable a Samba user: 

      [root@server ~]# smbpasswd -e user_name
Enabled user user_name.

    • Disable a Samba user: 

      [root@server ~]# smbpasswd -x user_name
Disabled user user_name

    • Delete a user: 

      [root@server ~]# smbpasswd -x user_name
Deleted user user_name.

Additional resources

  • smbpasswd(8) man page

1.20.9. Using the smbstatus utility

The smbstatus utility reports on:

  • Connections per PID of each smbd daemon to the Samba server. This report includes the user name, primary group, SMB protocol version, encryption, and signing information.
  • Connections per Samba share. This report includes the PID of the smbd daemon, the IP of the connecting machine, the time stamp when the connection was established, encryption, and signing information.
  • A list of locked files. The report entries include further details, such as opportunistic lock (oplock) types

Prerequisites

  • The samba package is installed.
  • The smbd service is running.

Procedure

# smbstatus

Samba version 4.15.2
PID  Username              Group                Machine                            Protocol Version  Encryption  Signing
....-------------------------------------------------------------------------------------------------------------------------
963  DOMAIN\administrator  DOMAIN\domain users  client-pc  (ipv4:192.0.2.1:57786)  SMB3_02           -           AES-128-CMAC

Service  pid  Machine    Connected at                  Encryption  Signing:
....---------------------------------------------------------------------------
example  969  192.0.2.1  Thu Nov  1 10:00:00 2018 CEST  -           AES-128-CMAC

Locked files:
Pid  Uid    DenyMode   Access    R/W     Oplock      SharePath           Name      Time
....--------------------------------------------------------------------------------------------------------
969  10000  DENY_WRITE 0x120089  RDONLY  LEASE(RWH)  /srv/samba/example  file.txt  Thu Nov  1 10:00:00 2018

Additional resources

  • smbstatus(1) man page

1.20.10. Using the smbtar utility

The smbtar utility backs up the content of an SMB share or a subdirectory of it and stores the content in a tar archive. Alternatively, you can write the content to a tape device.

Prerequisites

  • The samba-client package is installed.

Procedure

  • Use the following command to back up the content of the demo directory on the //server/example/ share and store the content in the /root/example.tar archive: 

    # smbtar -s server -x example -u user_name -p password -t /root/example.tar

Additional resources

  • smbtar(1) man page

1.20.11. Using the wbinfo utility

The wbinfo utility queries and returns information created and used by the winbindd service.

Prerequisites

  • The samba-winbind-clients package is installed.

Procedure

You can use wbinfo, for example, to:

  • List domain users: 

    # wbinfo -u
AD\administrator
AD\guest
...

  • List domain groups: 

    # wbinfo -g
AD\domain computers
AD\domain admins
AD\domain users
...

  • Display the SID of a user: 

    # wbinfo --name-to-sid="AD\administrator"
S-1-5-21-1762709870-351891212-3141221786-500 SID_USER (1)

  • Display information about domains and trusts: 

    # wbinfo --trusted-domains --verbose
Domain Name   DNS Domain            Trust Type  Transitive  In   Out
BUILTIN                             None        Yes         Yes  Yes
server                              None        Yes         Yes  Yes
DOMAIN1       domain1.example.com   None        Yes         Yes  Yes
DOMAIN2       domain2.example.com   External    No          Yes  Yes

Additional resources

  • wbinfo(1) man page

1.21. Additional resources

Chapter 2. Exporting NFS shares

As a system administrator, you can use the NFS server to share a directory on your system over network.

2.1. Introduction to NFS

This section explains the basic concepts of the NFS service.

A Network File System (NFS) allows remote hosts to mount file systems over a network and interact with those file systems as though they are mounted locally. This enables you to consolidate resources onto centralized servers on the network.

The NFS server refers to the /etc/exports configuration file to determine whether the client is allowed to access any exported file systems. Once verified, all file and directory operations are available to the user.

2.2. Supported NFS versions

This section lists versions of NFS supported in Red Hat Enterprise Linux and their features.

Currently, Red Hat Enterprise Linux 9 supports the following major versions of NFS:

  • NFS version 3 (NFSv3) supports safe asynchronous writes and is more robust at error handling than the previous NFSv2; it also supports 64-bit file sizes and offsets, allowing clients to access more than 2 GB of file data.
  • NFS version 4 (NFSv4) works through firewalls and on the Internet, no longer requires an rpcbind service, supports Access Control Lists (ACLs), and utilizes stateful operations.

NFS version 2 (NFSv2) is no longer supported by Red Hat.

Default NFS version

The default NFS version in Red Hat Enterprise Linux 9 is 4.2. NFS clients attempt to mount using NFSv4.2 by default, and fall back to NFSv4.1 when the server does not support NFSv4.2. The mount later falls back to NFSv4.0 and then to NFSv3.

Features of minor NFS versions

Following are the features of NFSv4.2 in Red Hat Enterprise Linux 9:

Server-side copy
Enables the NFS client to efficiently copy data without wasting network resources using the copy_file_range() system call.
Sparse files
Enables files to have one or more holes, which are unallocated or uninitialized data blocks consisting only of zeroes. The lseek() operation in NFSv4.2 supports seek_hole() and seek_data(), which enables applications to map out the location of holes in the sparse file.
Space reservation
Permits storage servers to reserve free space, which prohibits servers to run out of space. NFSv4.2 supports the allocate() operation to reserve space, the deallocate() operation to unreserve space, and the fallocate() operation to preallocate or deallocate space in a file.
Labeled NFS
Enforces data access rights and enables SELinux labels between a client and a server for individual files on an NFS file system.
Layout enhancements
Provides the layoutstats() operation, which enables some Parallel NFS (pNFS) servers to collect better performance statistics.

Following are the features of NFSv4.1:

  • Enhances performance and security of network, and also includes client-side support for pNFS.
  • No longer requires a separate TCP connection for callbacks, which allows an NFS server to grant delegations even when it cannot contact the client: for example, when NAT or a firewall interferes.
  • Provides exactly once semantics (except for reboot operations), preventing a previous issue whereby certain operations sometimes returned an inaccurate result if a reply was lost and the operation was sent twice.

2.3. The TCP and UDP protocols in NFSv3 and NFSv4

NFSv4 requires the Transmission Control Protocol (TCP) running over an IP network.

NFSv3 could also use the User Datagram Protocol (UDP) in earlier Red Hat Enterprise Linux versions. In Red Hat Enterprise Linux 9, NFS over UDP is no longer supported. By default, UDP is disabled in the NFS server.

2.4. Services required by NFS

This section lists system services that are required for running an NFS server or mounting NFS shares. Red Hat Enterprise Linux starts these services automatically.

Red Hat Enterprise Linux uses a combination of kernel-level support and service processes to provide NFS file sharing. All NFS versions rely on Remote Procedure Calls (RPC) between clients and servers. To share or mount NFS file systems, the following services work together depending on which version of NFS is implemented:

nfsd
The NFS server kernel module that services requests for shared NFS file systems.
rpcbind
Accepts port reservations from local RPC services. These ports are then made available (or advertised) so the corresponding remote RPC services can access them. The rpcbind service responds to requests for RPC services and sets up connections to the requested RPC service. This is not used with NFSv4.
rpc.mountd
This process is used by an NFS server to process MOUNT requests from NFSv3 clients. It checks that the requested NFS share is currently exported by the NFS server, and that the client is allowed to access it. If the mount request is allowed, the nfs-mountd service replies with a Success status and provides the File-Handle for this NFS share back to the NFS client.
rpc.nfsd
This process enables explicit NFS versions and protocols the server advertises to be defined. It works with the Linux kernel to meet the dynamic demands of NFS clients, such as providing server threads each time an NFS client connects. This process corresponds to the nfs-server service.
lockd
This is a kernel thread that runs on both clients and servers. It implements the Network Lock Manager (NLM) protocol, which enables NFSv3 clients to lock files on the server. It is started automatically whenever the NFS server is run and whenever an NFS file system is mounted.
rpc.statd
This process implements the Network Status Monitor (NSM) RPC protocol, which notifies NFS clients when an NFS server is restarted without being gracefully brought down. The rpc-statd service is started automatically by the nfs-server service, and does not require user configuration. This is not used with NFSv4.
rpc.rquotad
This process provides user quota information for remote users. The rpc-rquotad service, which is provided by the quota-rpc package, has to be started by user when the nfs-server is started.
rpc.idmapd

This process provides NFSv4 client and server upcalls, which map between on-the-wire NFSv4 names (strings in the form of user@domain) and local UIDs and GIDs. For idmapd to function with NFSv4, the /etc/idmapd.conf file must be configured. At a minimum, the Domain parameter should be specified, which defines the NFSv4 mapping domain. If the NFSv4 mapping domain is the same as the DNS domain name, this parameter can be skipped. The client and server must agree on the NFSv4 mapping domain for ID mapping to function properly.

Only the NFSv4 server uses rpc.idmapd, which is started by the nfs-idmapd service. The NFSv4 client uses the keyring-based nfsidmap utility, which is called by the kernel on-demand to perform ID mapping. If there is a problem with nfsidmap, the client falls back to using rpc.idmapd.

The RPC services with NFSv4

The mounting and locking protocols have been incorporated into the NFSv4 protocol. The server also listens on the well-known TCP port 2049. As such, NFSv4 does not need to interact with rpcbind, lockd, and rpc-statd services. The nfs-mountd service is still required on the NFS server to set up the exports, but is not involved in any over-the-wire operations.

Additional resources

2.5. NFS host name formats

This section describes different formats that you can use to specify a host when mounting or exporting an NFS share.

You can specify the host in the following formats:

Single machine

Either of the following:

  • A fully-qualified domain name (that can be resolved by the server)
  • Host name (that can be resolved by the server)
  • An IP address.
IP networks

Either of the following formats is valid:

  • a.b.c.d/z, where a.b.c.d is the network and z is the number of bits in the netmask; for example 192.168.0.0/24.
  • a.b.c.d/netmask, where a.b.c.d is the network and netmask is the netmask; for example, 192.168.100.8/255.255.255.0.
Netgroups
The @group-name format , where group-name is the NIS netgroup name.

2.6. NFS server configuration

This section describes the syntax and options of two ways to configure exports on an NFS server:

  • Manually editing the /etc/exports configuration file
  • Using the exportfs utility on the command line

2.6.1. The /etc/exports configuration file

The /etc/exports file controls which file systems are exported to remote hosts and specifies options. It follows the following syntax rules:

  • Blank lines are ignored.
  • To add a comment, start a line with the hash mark (#).
  • You can wrap long lines with a backslash (\).
  • Each exported file system should be on its own individual line.
  • Any lists of authorized hosts placed after an exported file system must be separated by space characters.
  • Options for each of the hosts must be placed in parentheses directly after the host identifier, without any spaces separating the host and the first parenthesis.
Export entry

Each entry for an exported file system has the following structure: 

export host(options)

It is also possible to specify multiple hosts, along with specific options for each host. To do so, list them on the same line as a space-delimited list, with each host name followed by its respective options (in parentheses), as in: 

export host1(options1) host2(options2) host3(options3)

In this structure:

export
The directory being exported
host
The host or network to which the export is being shared
options
The options to be used for host

Example 2.1. A simple /etc/exports file

In its simplest form, the /etc/exports file only specifies the exported directory and the hosts permitted to access it: 

/exported/directory bob.example.com

Here, bob.example.com can mount /exported/directory/ from the NFS server. Because no options are specified in this example, NFS uses default options.

Important

The format of the /etc/exports file is very precise, particularly in regards to use of the space character. Remember to always separate exported file systems from hosts and hosts from one another with a space character. However, there should be no other space characters in the file except on comment lines.

For example, the following two lines do not mean the same thing: 

/home bob.example.com(rw)
/home bob.example.com (rw)

The first line allows only users from bob.example.com read and write access to the /home directory. The second line allows users from bob.example.com to mount the directory as read-only (the default), while the rest of the world can mount it read/write.

Default options

The default options for an export entry are:

ro
The exported file system is read-only. Remote hosts cannot change the data shared on the file system. To allow hosts to make changes to the file system (that is, read and write), specify the rw option.
sync
The NFS server will not reply to requests before changes made by previous requests are written to disk. To enable asynchronous writes instead, specify the option async.
wdelay
The NFS server will delay writing to the disk if it suspects another write request is imminent. This can improve performance as it reduces the number of times the disk must be accessed by separate write commands, thereby reducing write overhead. To disable this, specify the no_wdelay option, which is available only if the default sync option is also specified.
root_squash

This prevents root users connected remotely (as opposed to locally) from having root privileges; instead, the NFS server assigns them the user ID nobody. This effectively "squashes" the power of the remote root user to the lowest local user, preventing possible unauthorized writes on the remote server. To disable root squashing, specify the no_root_squash option.

To squash every remote user (including root), use the all_squash option. To specify the user and group IDs that the NFS server should assign to remote users from a particular host, use the anonuid and anongid options, respectively, as in: 

export host(anonuid=uid,anongid=gid)

Here, uid and gid are user ID number and group ID number, respectively. The anonuid and anongid options enable you to create a special user and group account for remote NFS users to share.

By default, access control lists (ACLs) are supported by NFS under Red Hat Enterprise Linux. To disable this feature, specify the no_acl option when exporting the file system.

Default and overridden options

Each default for every exported file system must be explicitly overridden. For example, if the rw option is not specified, then the exported file system is shared as read-only. The following is a sample line from /etc/exports which overrides two default options: 

/another/exported/directory 192.168.0.3(rw,async)

In this example, 192.168.0.3 can mount /another/exported/directory/ read and write, and all writes to disk are asynchronous.

2.6.2. The exportfs utility

The exportfs utility enables the root user to selectively export or unexport directories without restarting the NFS service. When given the proper options, the exportfs utility writes the exported file systems to /var/lib/nfs/xtab. Because the nfs-mountd service refers to the xtab file when deciding access privileges to a file system, changes to the list of exported file systems take effect immediately.

Common exportfs options

The following is a list of commonly-used options available for exportfs:

-r
Causes all directories listed in /etc/exports to be exported by constructing a new export list in /var/lib/nfs/etab. This option effectively refreshes the export list with any changes made to /etc/exports.
-a
Causes all directories to be exported or unexported, depending on what other options are passed to exportfs. If no other options are specified, exportfs exports all file systems specified in /etc/exports.
-o file-systems
Specifies directories to be exported that are not listed in /etc/exports. Replace file-systems with additional file systems to be exported. These file systems must be formatted in the same way they are specified in /etc/exports. This option is often used to test an exported file system before adding it permanently to the list of exported file systems.
-i
Ignores /etc/exports; only options given from the command line are used to define exported file systems.
-u
Unexports all shared directories. The command exportfs -ua suspends NFS file sharing while keeping all NFS services up. To re-enable NFS sharing, use exportfs -r.
-v
Verbose operation, where the file systems being exported or unexported are displayed in greater detail when the exportfs command is executed.

If no options are passed to the exportfs utility, it displays a list of currently exported file systems.

Additional resources

2.7. NFS and rpcbind

The rpcbind service maps Remote Procedure Call (RPC) services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they expect to serve. The client system then contacts rpcbind on the server with a particular RPC program number. The rpcbind service redirects the client to the proper port number so it can communicate with the requested service.

The Network File System Version 3 (NFSv3) requires the rpcbind service.

Because RPC-based services rely on rpcbind to make all connections with incoming client requests, rpcbind must be available before any of these services start.

Access control rules for rpcbind affect all RPC-based services. Alternatively, it is possible to specify access control rules for each of the NFS RPC daemons.

Additional resources

  • rpc.mountd(8) man page
  • rpc.statd(8) man page

2.8. Installing NFS

This procedure installs all packages necessary to mount or export NFS shares.

Procedure

  • Install the nfs-utils package: 

    # dnf install nfs-utils

2.9. Starting the NFS server

This procedure describes how to start the NFS server, which is required to export NFS shares.

Prerequisites

  • For servers that support NFSv3 connections, the rpcbind service must be running. To verify that rpcbind is active, use the following command: 

    $ systemctl status rpcbind

    If the service is stopped, start and enable it: 

    $ systemctl enable --now rpcbind

Procedure

  • To start the NFS server and enable it to start automatically at boot, use the following command: 

    # systemctl enable --now nfs-server

Additional resources

2.10. Troubleshooting NFS and rpcbind

Because the rpcbind service provides coordination between RPC services and the port numbers used to communicate with them, it is useful to view the status of current RPC services using rpcbind when troubleshooting. The rpcinfo utility shows each RPC-based service with port numbers, an RPC program number, a version number, and an IP protocol type (TCP or UDP).

Procedure

  1. To make sure the proper NFS RPC-based services are enabled for rpcbind, use the following command: 

    # rpcinfo -p

    Example 2.2. rpcinfo -p command output

    The following is sample output from this command: 

       program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper
    100005    1   udp  20048  mountd
    100005    1   tcp  20048  mountd
    100005    2   udp  20048  mountd
    100005    2   tcp  20048  mountd
    100005    3   udp  20048  mountd
    100005    3   tcp  20048  mountd
    100024    1   udp  37769  status
    100024    1   tcp  49349  status
    100003    3   tcp   2049  nfs
    100003    4   tcp   2049  nfs
    100227    3   tcp   2049  nfs_acl
    100021    1   udp  56691  nlockmgr
    100021    3   udp  56691  nlockmgr
    100021    4   udp  56691  nlockmgr
    100021    1   tcp  46193  nlockmgr
    100021    3   tcp  46193  nlockmgr
    100021    4   tcp  46193  nlockmgr

    If one of the NFS services does not start up correctly, rpcbind will be unable to map RPC requests from clients for that service to the correct port.

  2. In many cases, if NFS is not present in rpcinfo output, restarting NFS causes the service to correctly register with rpcbind and begin working: 

    # systemctl restart nfs-server

Additional resources

2.11. Configuring the NFS server to run behind a firewall

NFS requires the rpcbind service, which dynamically assigns ports for RPC services and can cause issues for configuring firewall rules. The following sections describe how to configure NFS versions to work behind a firewall if you want to support:

  • NFSv3

    This includes any servers that support NFSv3:

    • NFSv3-only servers
    • Servers that support both NFSv3 and NFSv4
  • NFSv4-only

2.11.1. Configuring the NFSv3-enabled server to run behind a firewall

The following procedure describes how to configure servers that support NFSv3 to run behind a firewall. This includes NFSv3-only servers and servers that support both NFSv3 and NFSv4.

Procedure

  1. To allow clients to access NFS shares behind a firewall, configure the firewall by running the following commands on the NFS server: 

    firewall-cmd --permanent --add-service mountd
firewall-cmd --permanent --add-service rpc-bind
firewall-cmd --permanent --add-service nfs

  2. Specify the ports to be used by the RPC service nlockmgr in the /etc/nfs.conf file as follows: 

    [lockd]

port=tcp-port-number
udp-port=udp-port-number

    Alternatively, you can specify nlm_tcpport and nlm_udpport in the /etc/modprobe.d/lockd.conf file.

  3. Open the specified ports in the firewall by running the following commands on the NFS server: 

    firewall-cmd --permanent --add-port=<lockd-tcp-port>/tcp
firewall-cmd --permanent --add-port=<lockd-udp-port>/udp

  4. Add static ports for rpc.statd by editing the [statd] section of the /etc/nfs.conf file as follows: 

    [statd]

port=port-number

  5. Open the added ports in the firewall by running the following commands on the NFS server: 

    firewall-cmd --permanent --add-port=<statd-tcp-port>/tcp
firewall-cmd --permanent --add-port=<statd-udp-port>/udp

  6. Reload the firewall configuration: 

    firewall-cmd --reload

  7. Restart the rpc-statd service first, and then restart the nfs-server service: 

    # systemctl restart rpc-statd.service
# systemctl restart nfs-server.service

    Alternatively, if you specified the lockd ports in the /etc/modprobe.d/lockd.conf file:

    1. Update the current values of /proc/sys/fs/nfs/nlm_tcpport and /proc/sys/fs/nfs/nlm_udpport: 

      # sysctl -w fs.nfs.nlm_tcpport=<tcp-port>
# sysctl -w fs.nfs.nlm_udpport=<udp-port>

    2. Restart the rpc-statd and nfs-server services: 

      # systemctl restart rpc-statd.service
# systemctl restart nfs-server.service

2.11.2. Configuring the NFSv4-only server to run behind a firewall

The following procedure describes how to configure the NFSv4-only server to run behind a firewall.

Procedure

  1. To allow clients to access NFS shares behind a firewall, configure the firewall by running the following command on the NFS server: 

    firewall-cmd --permanent --add-service nfs

  2. Reload the firewall configuration: 

    firewall-cmd --reload

  3. Restart the nfs-server: 

    # systemctl restart nfs-server

2.11.3. Configuring an NFSv3 client to run behind a firewall

The procedure to configure an NFSv3 client to run behind a firewall is similar to the procedure to configure an NFSv3 server to run behind a firewall.

If the machine you are configuring is both an NFS client and an NFS server, follow the procedure described in Configuring the NFSv3-enabled server to run behind a firewall.

The following procedure describes how to configure a machine that is an NFS client only to run behind a firewall.

Procedure

  1. To allow the NFS server to perform callbacks to the NFS client when the client is behind a firewall, add the rpc-bind service to the firewall by running the following command on the NFS client: 

    firewall-cmd --permanent --add-service rpc-bind

  2. Specify the ports to be used by the RPC service nlockmgr in the /etc/nfs.conf file as follows: 

    [lockd]

port=port-number
udp-port=upd-port-number

    Alternatively, you can specify nlm_tcpport and nlm_udpport in the /etc/modprobe.d/lockd.conf file.

  3. Open the specified ports in the firewall by running the following commands on the NFS client: 

    firewall-cmd --permanent --add-port=<lockd-tcp-port>/tcp
firewall-cmd --permanent --add-port=<lockd-udp-port>/udp

  4. Add static ports for rpc.statd by editing the [statd] section of the /etc/nfs.conf file as follows: 

    [statd]

port=port-number

  5. Open the added ports in the firewall by running the following commands on the NFS client: 

    firewall-cmd --permanent --add-port=<statd-tcp-port>/tcp
firewall-cmd --permanent --add-port=<statd-udp-port>/udp

  6. Reload the firewall configuration: 

    firewall-cmd --reload

  7. Restart the rpc-statd service: 

    # systemctl restart rpc-statd.service

    Alternatively, if you specified the lockd ports in the /etc/modprobe.d/lockd.conf file:

    1. Update the current values of /proc/sys/fs/nfs/nlm_tcpport and /proc/sys/fs/nfs/nlm_udpport: 

      # sysctl -w fs.nfs.nlm_tcpport=<tcp-port>
# sysctl -w fs.nfs.nlm_udpport=<udp-port>

    2. Restart the rpc-statd service: 

      # systemctl restart rpc-statd.service

2.11.4. Configuring an NFSv4 client to run behind a firewall

Perform this procedure only if the client is using NFSv4.0. In that case, it is necessary to open a port for NFSv4.0 callbacks.

This procedure is not needed for NFSv4.1 or higher because in the later protocol versions the server performs callbacks on the same connection that was initiated by the client.

Procedure

  1. To allow NFSv4.0 callbacks to pass through firewalls, set /proc/sys/fs/nfs/nfs_callback_tcpport and allow the server to connect to that port on the client as follows: 

    # echo "fs.nfs.nfs_callback_tcpport = <callback-port>" >/etc/sysctl.d/90-nfs-callback-port.conf
# sysctl -p /etc/sysctl.d/90-nfs-callback-port.conf

  2. Open the specified port in the firewall by running the following command on the NFS client: 

    firewall-cmd --permanent --add-port=<callback-port>/tcp

  3. Reload the firewall configuration: 

    firewall-cmd --reload

2.12. Exporting RPC quota through a firewall

If you export a file system that uses disk quotas, you can use the quota Remote Procedure Call (RPC) service to provide disk quota data to NFS clients.

Procedure

  1. Enable and start the rpc-rquotad service: 

    # systemctl enable --now rpc-rquotad
    Note

    The rpc-rquotad service is, if enabled, started automatically after starting the nfs-server service.

  2. To make the quota RPC service accessible behind a firewall, the TCP (or UDP, if UDP is enabled) port 875 need to be open. The default port number is defined in the /etc/services file.

    You can override the default port number by appending -p port-number to the RPCRQUOTADOPTS variable in the /etc/sysconfig/rpc-rquotad file.

  3. By default, remote hosts can only read quotas. If you want to allow clients to set quotas, append the -S option to the RPCRQUOTADOPTS variable in the /etc/sysconfig/rpc-rquotad file.

  4. Restart rpc-rquotad for the changes in the /etc/sysconfig/rpc-rquotad file to take effect: 

    # systemctl restart rpc-rquotad

2.13. Enabling NFS over RDMA (NFSoRDMA)

In Red Hat Enterprise Linux 9, Remote direct memory access (RDMA) service on RDMA-capable hardware provides Network File System (NFS) protocol support for high-speed file transfer over the network.

Procedure

  1. Install the rdma-core package: 

    # dnf install rdma-core

  2. Verify the lines with xprtrdma and svcrdma are commented out in the /etc/rdma/modules/rdma.conf file: 

    # NFS over RDMA client support
xprtrdma
# NFS over RDMA server support
svcrdma

  3. On the NFS server, create directory /mnt/nfsordma and export it to /etc/exports: 

    # mkdir /mnt/nfsordma
# echo "/mnt/nfsordma *(fsid=0,rw,async,insecure,no_root_squash)" >> /etc/exports

  4. On the NFS client, mount the nfs-share with server IP address, for example, 172.31.0.186: 

    # mount -o rdma,port=20049 172.31.0.186:/mnt/nfs-share /mnt/nfs

  5. Restart the nfs-server service: 

    # systemctl restart nfs-server

Additional resources

2.14. Additional resources

Chapter 3. Securing NFS

To minimize NFS security risks and protect data on the server, consider the following sections when exporting NFS file systems on a server or mounting them on a client.

3.1. NFS security with AUTH_SYS and export controls

NFS provides the following traditional options in order to control access to exported files:

  • The server restricts which hosts are allowed to mount which file systems either by IP address or by host name.
  • The server enforces file system permissions for users on NFS clients in the same way it does for local users. Traditionally, NFS does this using the AUTH_SYS call message (also called AUTH_UNIX), which relies on the client to state the UID and GIDs of the user. Be aware that this means that a malicious or misconfigured client might easily get this wrong and allow a user access to files that it should not.

To limit the potential risks, administrators often limits the access to read-only or squash user permissions to a common user and group ID. Unfortunately, these solutions prevent the NFS share from being used in the way it was originally intended.

Additionally, if an attacker gains control of the DNS server used by the system exporting the NFS file system, they can point the system associated with a particular hostname or fully qualified domain name to an unauthorized machine. At this point, the unauthorized machine is the system permitted to mount the NFS share, because no username or password information is exchanged to provide additional security for the NFS mount.

Wildcards should be used sparingly when exporting directories through NFS, as it is possible for the scope of the wildcard to encompass more systems than intended.

Additional resources

  • To secure NFS and rpcbind, use, for example, nftables and firewalld.
  • nft(8) man page
  • firewalld-cmd(1) man page

3.2. NFS security with AUTH_GSS

All version of NFS support RPCSEC_GSS and the Kerberos mechanism.

Unlike AUTH_SYS, with the RPCSEC_GSS Kerberos mechanism, the server does not depend on the client to correctly represent which user is accessing the file. Instead, cryptography is used to authenticate users to the server, which prevents a malicious client from impersonating a user without having that user’s Kerberos credentials. Using the RPCSEC_GSS Kerberos mechanism is the most straightforward way to secure mounts because after configuring Kerberos, no additional setup is needed.

3.3. Configuring an NFS server and client to use Kerberos

Kerberos is a network authentication system that allows clients and servers to authenticate to each other by using symmetric encryption and a trusted third party, the KDC. Red Hat recommends using Identity Management (IdM) for setting up Kerberos.

Prerequisites

  • The Kerberos Key Distribution Centre (KDC) is installed and configured.

Procedure

    • Create the nfs/hostname.domain@REALM principal on the NFS server side.
    • Create the host/hostname.domain@REALM principal on both the server and the client side.
    • Add the corresponding keys to keytabs for the client and server.

  2. On the server side, use the sec= option to enable the wanted security flavors. To enable all security flavors as well as non-cryptographic mounts: 

    /export *(sec=sys:krb5:krb5i:krb5p)

    Valid security flavors to use with the sec= option are:

    • sys: no cryptographic protection, the default
    • krb5: authentication only

    • krb5i: integrity protection

      • uses Kerberos V5 for user authentication and performs integrity checking of NFS operations using secure checksums to prevent data tampering.

    • krb5p: privacy protection

      • uses Kerberos V5 for user authentication, integrity checking, and encrypts NFS traffic to prevent traffic sniffing. This is the most secure setting, but it also involves the most performance overhead.

  3. On the client side, add sec=krb5 (or sec=krb5i, or sec=krb5p, depending on the setup) to the mount options: 

    # mount -o sec=krb5 server:/export /mnt

Additional resources

3.4. NFSv4 security options

NFSv4 includes ACL support based on the Microsoft Windows NT model, not the POSIX model, because of the Microsoft Windows NT model’s features and wide deployment.

Another important security feature of NFSv4 is the removal of the use of the MOUNT protocol for mounting file systems. The MOUNT protocol presented a security risk because of the way the protocol processed file handles.

3.5. File permissions on mounted NFS exports

Once the NFS file system is mounted as either read or read and write by a remote host, the only protection each shared file has is its permissions. If two users that share the same user ID value mount the same NFS file system on different client systems, they can modify each others' files. Additionally, anyone logged in as root on the client system can use the su - command to access any files with the NFS share.

By default, access control lists (ACLs) are supported by NFS under Red Hat Enterprise Linux. Red Hat recommends to keep this feature enabled.

By default, NFS uses root squashing when exporting a file system. This sets the user ID of anyone accessing the NFS share as the root user on their local machine to nobody. Root squashing is controlled by the default option root_squash; for more information about this option, see NFS server configuration.

When exporting an NFS share as read-only, consider using the all_squash option. This option makes every user accessing the exported file system take the user ID of the nobody user.

Chapter 4. Enabling pNFS SCSI layouts in NFS

You can configure the NFS server and client to use the pNFS SCSI layout for accessing data. pNFS SCSI is beneficial in use cases that involve longer-duration single-client access to a file.

Prerequisites

  • Both the client and the server must be able to send SCSI commands to the same block device. That is, the block device must be on a shared SCSI bus.
  • The block device must contain an XFS file system.
  • The SCSI device must support SCSI Persistent Reservations as described in the SCSI-3 Primary Commands specification.

4.1. The pNFS technology

The pNFS architecture improves the scalability of NFS. When a server implements pNFS, the client is able to access data through multiple servers concurrently. This can lead to performance improvements.

pNFS supports the following storage protocols or layouts on RHEL:

  • Files
  • Flexfiles
  • SCSI

4.2. pNFS SCSI layouts

The SCSI layout builds on the work of pNFS block layouts. The layout is defined across SCSI devices. It contains a sequential series of fixed-size blocks as logical units (LUs) that must be capable of supporting SCSI persistent reservations. The LU devices are identified by their SCSI device identification.

pNFS SCSI performs well in use cases that involve longer-duration single-client access to a file. An example might be a mail server or a virtual machine housing a cluster.

Operations between the client and the server

When an NFS client reads from a file or writes to it, the client performs a LAYOUTGET operation. The server responds with the location of the file on the SCSI device. The client might need to perform an additional operation of GETDEVICEINFO to determine which SCSI device to use. If these operations work correctly, the client can issue I/O requests directly to the SCSI device instead of sending READ and WRITE operations to the server.

Errors or contention between clients might cause the server to recall layouts or not issue them to the clients. In those cases, the clients fall back to issuing READ and WRITE operations to the server instead of sending I/O requests directly to the SCSI device.

To monitor the operations, see Monitoring pNFS SCSI layouts functionality.

Device reservations

pNFS SCSI handles fencing through the assignment of reservations. Before the server issues layouts to clients, it reserves the SCSI device to ensure that only registered clients may access the device. If a client can issue commands to that SCSI device but is not registered with the device, many operations from the client on that device fail. For example, the blkid command on the client fails to show the UUID of the XFS file system if the server has not given a layout for that device to the client.

The server does not remove its own persistent reservation. This protects the data within the file system on the device across restarts of clients and servers. In order to repurpose the SCSI device, you might need to manually remove the persistent reservation on the NFS server.

4.3. Checking for a SCSI device compatible with pNFS

This procedure checks if a SCSI device supports the pNFS SCSI layout.

Prerequisites

  • Install the sg3_utils package: 

    # dnf install sg3_utils

Procedure

  • On both the server and client, check for the proper SCSI device support: 

    # sg_persist --in --report-capabilities --verbose path-to-scsi-device

    Ensure that the Persist Through Power Loss Active (PTPL_A) bit is set.

    Example 4.1. A SCSI device that supports pNFS SCSI

    The following is an example of sg_persist output for a SCSI device that supports pNFS SCSI. The PTPL_A bit reports 1. 

        inquiry cdb: 12 00 00 00 24 00
    Persistent Reservation In cmd: 5e 02 00 00 00 00 00 20 00 00
  LIO-ORG   block11           4.0
  Peripheral device type: disk
Report capabilities response:
  Compatible Reservation Handling(CRH): 1
  Specify Initiator Ports Capable(SIP_C): 1
  All Target Ports Capable(ATP_C): 1
  Persist Through Power Loss Capable(PTPL_C): 1
  Type Mask Valid(TMV): 1
  Allow Commands: 1
  Persist Through Power Loss Active(PTPL_A): 1
    Support indicated in Type mask:
      Write Exclusive, all registrants: 1
      Exclusive Access, registrants only: 1
      Write Exclusive, registrants only: 1
      Exclusive Access: 1
      Write Exclusive: 1
      Exclusive Access, all registrants: 1

Additional resources

  • sg_persist(8) man page

4.4. Setting up pNFS SCSI on the server

This procedure configures an NFS server to export a pNFS SCSI layout.

Procedure

  1. On the server, mount the XFS file system created on the SCSI device.

  2. Configure the NFS server to export NFS version 4.1 or higher. Set the following option in the [nfsd] section of the /etc/nfs.conf file: 

    [nfsd]

vers4.1=y

  3. Configure the NFS server to export the XFS file system over NFS with the pnfs option:

    Example 4.2. An entry in /etc/exports to export pNFS SCSI

    The following entry in the /etc/exports configuration file exports the file system mounted at /exported/directory/ to the allowed.example.com client as a pNFS SCSI layout: 

    /exported/directory allowed.example.com(pnfs)
    Note

    The exported file system must be created on the whole block device, not only on a partition.

Additional resources

4.5. Setting up pNFS SCSI on the client

This procedure configures an NFS client to mount a pNFS SCSI layout.

Prerequisites

Procedure

  • On the client, mount the exported XFS file system using NFS version 4.1 or higher: 

    # mount -t nfs -o nfsvers=4.1 host:/remote/export /local/directory

    Do not mount the XFS file system directly without NFS.

Additional resources

4.6. Releasing the pNFS SCSI reservation on the server

This procedure releases the persistent reservation that an NFS server holds on a SCSI device. This enables you to repurpose the SCSI device when you no longer need to export pNFS SCSI.

You must remove the reservation from the server. It cannot be removed from a different IT Nexus.

Prerequisites

  • Install the sg3_utils package: 

    # dnf install sg3_utils

Procedure

  1. Query an existing reservation on the server: 

    # sg_persist --read-reservation path-to-scsi-device

    Example 4.3. Querying a reservation on /dev/sda

    # *sg_persist --read-reservation /dev/sda*

  LIO-ORG   block_1           4.0
  Peripheral device type: disk
  PR generation=0x8, Reservation follows:
    Key=0x100000000000000
    scope: LU_SCOPE,  type: Exclusive Access, registrants only

  2. Remove the existing registration on the server: 

    # sg_persist --out \
             --release \
             --param-rk=reservation-key \
             --prout-type=6 \
             path-to-scsi-device

    Example 4.4. Removing a reservation on /dev/sda

    # sg_persist --out \
             --release \
             --param-rk=0x100000000000000 \
             --prout-type=6 \
             /dev/sda

  LIO-ORG   block_1           4.0
  Peripheral device type: disk

Additional resources

  • sg_persist(8) man page

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