Chapter 1. Getting Started

This chapter covers the basic tasks that you might need to perform just after you have installed Red Hat Enterprise Linux 7.

Note that these items may include tasks that are usually done already during the installation proces, but they do not have to be done necessarily, such as the registration of the system. The subchapters dealing with such tasks provide a brief summary of how this can be achived during the installation and links to related documentation in a special section.

For detailed information on Red Hat Enterprise Linux 7 installation, consult Red Hat Enterprise Linux 7 Installation Guide.

Note

This chapter mentions some commands to be performed. The commands that need to be entered by the root user have # in the prompt, while the commands that can be performed by a regular user, have $ in their prompt.

For further information on common post-installation tasks, you can see also Red Hat Enterprise Linux 7 Installation Guide.

Although all post-installation tasks can be achieved through the command line, you can also use the Cockpit tool to perform some of them.

What Cockpit Is and Which Tasks It Can Be Used For

Cockpit is a system administration tool that provides a user interface for monitoring and administering servers through a web browser.

Cockpit enables to perform these tasks:

  • Monitoring basic system features, such as hardware, internet connection, or performance characteristics
  • Analyzing the content of the system log files
  • Configuring basic networking features, such as interfaces, network logs, packet sizes
  • Managing user accounts
  • Monitoring and configuring system services
  • Creating diagnostic reports
  • Setting kernel dump configuration
  • Configuring SELinux
  • Managing system subscriptions
  • Accessing the terminal

For more information on installing and using Cockpit, see Red Hat Enterprise Linux 7 Getting Started with Cockpit Guide.

1.1. Basic Configuration of the Environment

Basic configuration of the environment includes:

  • Date and Time
  • System Locales
  • Keyboard Layout

Setting of these items is normally a part of the installation process.

For more information, see the appropriate source according to the installation method:

If you need to reconfigure the basic characteristics of the environment after the installation, follow the instructions in this section.

1.1.1. Introduction to Configuring the Date and Time

Accurate time keeping is important for a number of reasons. In Red Hat Enterprise Linux 7, time keeping is ensured by the NTP protocol, which is implemented by a daemon running in user space. The user space daemon updates the system clock running in the kernel. The system clock can keep time by using various clock sources.

Red Hat Enterprise Linux 7 uses the following daemons to implement NTP:

If you want to use ntpd instead of default chronyd, you need to disable chronyd, install, enable and configure ntpd as shown in Chapter 19, Configuring NTP Using ntpd.

Displaying the Current Date and Time

To display the current date and time, use one of the following commands:

~]$ date
~]$ timedatectl

Note that the timedatectl command provides more verbose output, including universal time, currently used time zone, the status of the Network Time Protocol (NTP) configuration, and some additional information.

For more information on configuring the date and time, see Chapter 3, Configuring the Date and Time.

1.1.2. Introduction to Configuring the System Locale

System-wide locale settings are stored in the /etc/locale.conf file, which is read at early boot by the systemd daemon. The locale settings configured in /etc/locale.conf are inherited by every service or user, unless individual programs or individual users override them.

Basic tasks to handle the system locales:

  • Listing available system locale settings:

    ~]$ localectl list-locales
  • Displaying current status of the system locales settings:

    ~]$ localectl status
  • Setting or changing the default system locale settings:

    ~]# localectl set-locale LANG=locale

For more information on configuring the system locale, see Chapter 2, System Locale and Keyboard Configuration.

1.1.3. Introduction to Configuring the Keyboard Layout

The keyboard layout settings control the layout used on the text console and graphical user interfaces.

Basic tasks to handle the keyboard layout include:

  • Listing available keymaps:

    ~]$ localectl list-keymaps
  • Displaying current status of keymap settings:

    ~]$ localectl status
  • Setting or changing the default system keymap:

    ~]# localectl set-keymap

For more information on configuring the keyboard layout, see Chapter 2, System Locale and Keyboard Configuration.

1.2. Configuring and Inspecting Network Access

The network access is usually configured during the installation process. However, the installation process does not prompt you to configure network interfaces on some common installation paths. Consequently, it is possible that the network access is not configured after the installation. If this happens, you can configure network access after installation.

For a quickstart to configuring network access during the installation, see Section 1.2.1, “Configuring Network Access During the Installation Process”. To configure network access after the installation, you can use either the nmcli command-line utility, described in Red Hat Enterprise Linux 7 Networking Guide or the nmtui text user interface utility, described in Red Hat Enterprise Linux 7 Networking Guide.

The nmcli and nmtui utilities also enable you to add one or more new network connections, as well as modify and inspect the existing connections. If you want to create and manage network connections with nmcli, see Section 1.2.2, “Managing Network Connections After the Installation Process Using nmcli”. If you want to create and manage network connections with nmtui, see Section 1.2.3, “Managing Network Connections After the Installation Process Using nmtui”.

1.2.1. Configuring Network Access During the Installation Process

Ways to configure network access during the installation proces:

  • The Network & Hostname menu at the Installation Summary screen in the graphical user interface of the Anaconda installation program
  • The Network settings option in the text mode of the Anaconda installation program
  • The Kickstart file

When the system boots for the first time after the installation has finished, any network interfaces which you configured during the installation are automatically activated.

For detailed information on configuration of network access during installation process, see Red Hat Enterprise Linux 7 Installation Guide.

1.2.2. Managing Network Connections After the Installation Process Using nmcli

Run the following commands as the root user to manage network connections using the nmcli utility.

To create a new connection:

~]# nmcli con add type type of the connection "con-name" connection name ifname ifname interface-name the name of the interface ipv4 address ipv4 address gw4 address gateway address

To modify the existing connection:

~]# nmcli con mod "con-name"

To display all connections:

~]# nmcli con show

To display the active connection:

~]# nmcli con show --active

To display all configuration settings of a particular connection:

~]# nmcli con show "con-name"

For more information on the nmcli command-line utility, see Red Hat Enterprise Linux 7 Networking Guide.

1.2.3. Managing Network Connections After the Installation Process Using nmtui

The NetworkManager text user interface (TUI) utility, nmtui, provides a text interface to configure networking by controlling NetworkManager.

For more information about installing and using the nmtui text interface tool, see Red Hat Enterprise Linux 7 Networking Guide.

1.2.4. Managing Networking in Cockpit

In Cockpit, the Networking menu enables you:

  • To display currently received and sent packets
  • To display the most important characteristics of available network interfaces
  • To display content of the networking logs.
  • To add various types of network interfaces (bond, team, bridge, VLAN)

Figure 1.1. Managing Networking in Cockpit

Networking n

1.3. The Basics of Registering the System and Managing Subscriptions

1.3.1. What Red Hat Subscriptions Are and Which Tasks They Can Be Used For

The products installed on Red Hat Enterprise Linux 7, including the operating system itself, are covered by subscriptions.

A subscription to Red Hat Content Delivery Network is used to track:

  • Registered systems
  • Products installed on those system
  • Subscriptions attached to those product

1.3.2. Registering the System During the Installation

This section provides a brief summary of registering Red Hat Enterprise Linux 7 during the installation process. If your operating system is not registered after the installation, you can find what might have been missed during the installation by reading through this section. For detailed information, consult Red Hat Enterprise Linux 7 Installation Guide.

Basically, there are two ways to register the system during the installation:

  • Normally, registration is a part of the Initial Setup configuration process. For more information, see Red Hat Enterprise Linux 7 Installation Guide.
  • Another option is to run Subscription manager as a post-installation script, which performs the automatic registration at the moment when the installation is complete and before the system is rebooted for the first time. To ensure this, modify the %post section of the Kickstart file. For more detailed information on running Subscription manager as a post-installation script, see Red Hat Enterprise Linux 7 Installation Guide.

1.3.3. Registering the System after the Installation

If you have not registered your system during installation process, you can do it afterwards by applying the following procedure. Note that all commands in this procedure need to be performed as the root user.

Registering and Subscribing Your System

  1. Register your system:

    ~]# subscription-manager register

    The command will prompt you to enter your Red Hat Customer Portal user name and password.

  2. Determine the pool ID of a subscription that you require:

    ~]# subscription-manager list --available

    This command displays all available subscriptions for your Red Hat account. For every subscription, various characteristics are displayed, including the pool ID.

  3. Attach the appropriate subscription to your system by replacing pool_id with the pool ID determined in the previous step:

    ~]# subscription-manager attach --pool=pool_id

For more information on registration of your system and attachment of the Red Hat Content Delivery Network subscriptions, see Chapter 7, Registering the System and Managing Subscriptions.

1.3.4. Registering a System to EUS Content

To access the Extended Update Support (EUS) content, register your system as follows:

  1. Verify that EUS entitlements are available:

    ~]# subscription-manager list --available --matches="Extended Update Support"
        +-------------------------------------------+
            Available Subscriptions
        +-------------------------------------------+
        Subscription Name:   Extended Update Support
        Provides:            Red Hat Enterprise Linux High Availability for x86_64 - Extended Update Support
                             Red Hat Enterprise Linux Resilient Storage for x86_64 - Extended Update Support
                             Red Hat Enterprise Linux for x86_64 - Extended Update Support
                             Red Hat EUCJP Support (for RHEL Server) - Extended Update Support
                             RHEL for SAP - Extended Update Support
                             Red Hat Enterprise Linux Load Balancer (for RHEL Server) - Extended Update Support
                             Red Hat Enterprise Linux Scalable File System (for RHEL Server) - Extended Update Support
                             Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support
                             RHEL for SAP HANA - Extended Update Support
                             Red Hat Enterprise Linux High Performance Networking (for RHEL Server) - Extended Update Support
                             Oracle Java (for RHEL Server) - Extended Update Support
                             Red Hat S-JIS Support (for RHEL Server) - Extended Update Support
        SKU:                 RH00030
        Contract:            12069074
        Pool ID:             8a99f9ac7238188b01723d9c8a8a06a9
        Provides Management: No
        Available:           8
        Suggested:           0
        Service Level:       Layered
        Service Type:        L1-L3
        Subscription Type:   Instance Based
        Starts:              05/22/2020
        Ends:                05/21/2021
        System Type:         Physical
  2. Attach the applicable subscription using the Pool identifier:

    ~]# subscription-manager attach --pool 8a99f9ac7238188b01723d9c8a8a06a9
  3. Replace the default repositories enabled for the system with the EUS variants:

    ~]# subscription-manager repos --disable \*
  4. Enable the repositories which represent the EUS content set for the RHEL revision in use:

    ~]# subscription-manager repos --enable rhel-7-server-eus-rpms
  5. Select the required and supported release for the end system:

    ~]# subscription-manager release --set 7.6

For currently supported EUS releases, see Extended Update Support Add-on.

1.4. Installing Software

This section provides information to guide you through the basics of software installation on a Red Hat Enterprise Linux 7 system. It mentions the prerequisites that you need to fulfil to be able to install software in Section 1.4.1, “Prerequisites for Software Installation”, provides the basic information on software packaging and software repositories in Section 1.4.2, “Introduction to the System of Software Packaging and Software Repositories”, and references the ways to perform basic tasks related to software installation in Section 1.4.3, “Managing Basic Software Installation Tasks with Subscription Manager and Yum”.

1.4.1. Prerequisites for Software Installation

The Red Hat Content Delivery Network subscription service provides a mechanism to handle Red Hat software inventory and enables you to install additional software or update already installed packages. You can start installing software once you have registered your system and attached a subscription, as described in Section 1.3, “The Basics of Registering the System and Managing Subscriptions”.

1.4.2. Introduction to the System of Software Packaging and Software Repositories

All software on a Red Hat Enterprise Linux system is divided into RPM packages, which are stored in particular repositories. When a system is subscribed to the Red Hat Content Delivery Network, a repository file is created in the /etc/yum.repos.d/ directory.

Use the yum utility to manage package operations:

  • Searching information about packages
  • Installing packages
  • Updating packages
  • Removing packages
  • Checking the list of currently available repositories
  • Adding or removing a repository
  • Enabling or disabling a repository

For information on basic tasks related to the installation of software, see Section 1.4.3, “Managing Basic Software Installation Tasks with Subscription Manager and Yum”. For further information on managing software repositories, see Section 7.2, “Managing Software Repositories”. For detailed information on using the yum utility, see Chapter 9, Yum.

1.4.3. Managing Basic Software Installation Tasks with Subscription Manager and Yum

The most basic software-installation tasks that you might need after the operating system has been installed include:

  • Listing all available repositories:

    ~]# subscription-manager repos --list
  • Listing all currently enabled repositories:

    ~]$ yum repolist
  • Enabling or disabling a repository:

    ~]# subscription-manager repos --enable repository
    ~]# subscription-manager repos --disable repository
  • Searching for packages matching a specific string:

    ~]$ yum search string
  • Installing a package:

    ~]# yum install package_name
  • Updating all packages and their dependencies:

    ~]# yum update
  • Updating a package:

    ~]# yum update package_name
  • Uninstalling a package and any packages that depend on it:

    ~]# yum remove package_name
  • Listing information on all installed and available packages:

    ~]$ yum list all
  • Listing information on all installed packages:

    ~]$ yum list installed

1.5. Making systemd Services Start at Boot Time

Systemd is a system and service manager for Linux operating systems that introduces the concept of systemd units. For more information on systemd, see Section 10.1, “Introduction to systemd”.

This section provides the information on how to ensure that a service is enabled or disabled at boot time. It also explains how to manage the services through Cockpit.

1.5.1. Enabling or Disabling the Services

You can determine services that are enabled or disabled at boot time already during the installation process, or you can enable or disable a service on an installed operating system.

To create the list of services enabled or disabled at boot time during the installation process, use the services option in the Kickstart file:

services [--disabled=list] [--enabled=list]
Note

The list of disabled services is processed before the list of enabled services. Therefore, if a service appears on both lists, it will be enabled. The list of the services should be given in the comma separated format. Do not include spaces in the list of services. For detailed information, refer to Red Hat Enterprise Linux 7 Installation Guide.

To enable or disable a service on an already installed operating system:

~]# systemctl enableservice_name
~]# systemctl disableservice_name

For further details, see Section 10.2, “Managing System Services”.

1.5.2. Managing Services in Cockpit

In Cockpit, select Services to manage systemd targets, services, sockets, timers and paths. There you can check their status, start or stop them, enable or disable them.

Figure 1.2. Managing Services in Cockpit

systemd n

1.5.3. Additional Resources on systemd Services

For more information on systemd, see Chapter 10, Managing Services with systemd.

1.6. Enhancing System Security with a Firewall, SELinux and SSH Logings

Computer security is the protection of computer systems from the theft or damage to their hardware, software, or information, as well as from disruption or misdirection of the services they provide. Ensuring computer security is therefore an essential task not only in the enterprises processing sensitive data or handling some business transactions.

Computer security includes a wide variety of features and tools. This section covers only the basic security features that you need to configure after you have installed the operating system. For detailed information on securing Red Hat Enterprise Linux 7, see Red Hat Enterprise Linux 7 Security Guide.

1.6.1. Ensuring the Firewall Is Enabled and Running

1.6.1.1. What a Firewall Is and How It Enhances System Security

A firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network.

On Red Hat Enterprise Linux 7, the firewall is provided by the firewalld service, which is automatically enabled during the installation of Red Hat Enterprise Linux. However, if you explicitly disabled the service, for example in the kickstart configuration, you can re-enable it, as described in Section 1.6.1.2, “Re-enabling the firewalld Service”. For overview of firewall setting options in the Kickstart file, see Red Hat Enterprise Linux 7 Installation Guide.

1.6.1.2. Re-enabling the firewalld Service

In case that the firewalld service is disabled after the installation, Red Hat recommends to consider re-enabling it.

You can display the current status of firewalld even as a regular user:

~]$ systemctl status firewalld

If firewalld is not enabled and running, switch to the root user, and change its status:

~]# systemctl start firewalld
~]# systemctl enable firewalld

For further information on post-installation procedures related to firewalld, see Red Hat Enterprise Linux 7 Security Guide. For detailed information on configuring and using firewall, see Red Hat Enterprise Linux 7 Security Guide

1.6.2. Ensuring the Appropriate State of SELinux

1.6.2.1. What SELinux Is and How It Enhances System Security

Security Enhanced Linux (SELinux) is an additional layer of system security that determines which process can access which files, directories, and ports.

SELinux States

SELinux has two possible states:

  • Enabled
  • Disabled

When SELinux is disabled, only Discretionary Access Control (DAC) rules are used.

SELinux Modes

When SELinux is enabled, it can run in one of the following modes:

  • Enforcing
  • Permissive

Enforcing mode means that SELinux policies is enforced. SELinux denies access based on SELinux policy rules, and enables only the interactions that are particularly allowed. Enforcing mode is the default mode after the installation and it is also the safest SELinux mode.

Permissive mode means that SELinux policies is not enforced. SELinux does not deny access, but denials are logged for actions that would have been denied if running in enforcing mode. Permissive mode is the default mode during the installation. Operating in permissive mode is also useful in some specific cases, for example if you require access to the Access Vector Cache (AVC) denials when troubleshooting problems.

For further information on SELinux in Red Hat Enterprise Linux 7, see Red Hat Enterprise Linux 7 SELinux User’s and Administrator’s Guide.

1.6.2.2. Ensuring the Required State of SELinux

By default, SELinux operates in permissive mode during the installation and in enforcing mode when the installation has finished.

However, in some specific situations, SELinux might be explicitly set to permissive mode or it might even be disabled on the installed operating system. This can be set for example in the kickstart configuration. For overview of SELinux setting options in the Kickstart file, see Red Hat Enterprise Linux 7 Installation Guide.

Important

Red Hat recommends to keep your system in enforcing mode.

To display the current SELinux mode, and to set the mode as needed:

Ensuring the Required State of SELinux

  1. Display the current SELinux mode in effect:

    ~]$ getenforce
  2. If needed, switch between the SELinux modes.

    The switch can be either temporary or permanent. A temporary switch is not persistent across reboots, while permanent switch is.

    • To temporary switch to either enforcing or permissive mode:

      ~]# setenforce Enforcing
      ~]# setenforce Permissive
    • To permanently set the SELinux mode, modify the SELINUX variable in the /etc/selinux/config configuration file.

      For example, to switch SELinux to enforcing mode:

      # This file controls the state of SELinux on the system.
      # SELINUX= can take one of these three values:
      #   enforcing - SELinux security policy is enforced.
      #   permissive - SELinux prints warnings instead of enforcing.
      #   disabled - No SELinux policy is loaded.
      SELINUX=enforcing

1.6.2.3. Managing SELinux in Cockpit

In Cockpit, use the SELinux option to turn SELinux enforcing policy on or off.

By default, SELinux enforcing policy in Cockpit is on, and SELinux operates in enforcing mode. By turning it off, you can switch SELinux into permissive mode. Note that such deviation from the default configuration in the /etc/sysconfig/selinux file is automatically reverted on the next boot.

Figure 1.3. Managing SELinux in Cockpit

selinux on n

1.6.3. Using SSH-based Authentication

1.6.3.1. What SSH-based Authentication Is and How It Enhances System Security

If you want to secure your communication with another computer, you can use SSH-based authentication.

Secure Shell (SSH) is a protocol which facilitates client-server communication and allows users to log in to any host system running SSH remotely. SSH encrypts the connection. The client transmits its authentication information to the server using encryption, and all data sent and received during a session are transferred under the encryption.

SSH enables its users to authenticate without a password. To do so, SSH uses a private-public key scheme.

For further information about SSH safeguards, see Section 12.1.2, “Main Features”.

1.6.3.2. Establishing an SSH Connection

To be able to use SSH connection, create a pair of two keys consisting of a public and a private key.

Creating the Key Files and Copying Them to the Server

  1. Generate a public and a private key:

    ~]$ ssh-keygen

    Both keys are stored in the ~/.ssh/ directory:

    • ~/.ssh/id_rsa.pub - public key
    • ~/.ssh/id_rsa - private key

      The public key does not need to be secret. It is used to verify the private key. The private key is secret. You can choose to protect the private key with the passphrase that you specify during the key generation process. With the passphrase, authentication is even more secure, but is no longer password-less. You can avoid this using the ssh-agent command. In this case, you will enter the passphrase only once - at the beginning of a session. For more information on ssh-agent configuration, see Section 12.2.4, “Using Key-based Authentication”.

  2. Copy the most recently modified public key to a remote machine you want to log into:

    ~]# ssh-copy-id USER@hostname

    As a result, you are now able to enter the system in a secure way, but without entering a password.

1.6.3.3. Disabling SSH Root Login

To increase system security, you can disable SSH access for the root user, which is enabled by default.

For more information on this topic, see Red Hat Enterprise Linux 7 Security Guide.

Disabling SSH Root Login

  1. Access the /etc/ssh/sshd_config file:

    ~]# vi /etc/ssh/sshd_config
  2. Change the line that reads #PermitRootLogin yes to:

    PermitRootLogin no
  3. Restart the sshd service:

    ~]# systemctl restart sshd

1.7. The Basics of Managing User Accounts

Red Hat Enterprise Linux 7 is a multi-user operating system, which enables multiple users on different computers to access a single system installed on one machine. Every user operates under its own account, and managing user accounts thus represents a core element of Red Hat Enterprise Linux system administration.

Normal and System Accounts

Normal accounts are created for users of a particular system. Such accounts can be added, removed, and modified during normal system administration.

System accounts represent a particular applications identifier on a system. Such accounts are generally added or manipulated only at software installation time, and they are not modified later.

Warning

System accounts are presumed to be available locally on a system. If these accounts are configured and provided remotely, such as in the instance of an LDAP configuration, system breakage and service start failures can occur.

For system accounts, user IDs below 1000 are reserved. For normal accounts, you can use IDs starting at 1000. However, the recommended practice is to assign IDs starting at 5000. See Section 4.1, “Introduction to Users and Groups” for more information. The guidelines for assigning IDs can be found in the /etc/login.defs file.

# Min/max values for automatic uid selection in useradd
#
UID_MIN         1000
UID_MAX         60000
# System accounts
SYS_UID_MIN        201
SYS_UID_MAX        999

What Groups Are and Which Purposes They Can Be Used For

A group is an entity which ties together multiple user accounts for a common purpose, such as granting access to particular files.

1.7.1. The Most Basic Command-Line Tools to Manage User Accounts and Groups

The most basic tasks to manage user accounts and groups, and the appropriate command-line tools, include:

  • Displaying user and group IDs:

    ~]$ id
  • Creating a new user account:

    ~]# useradd [options] user_name
  • Assigning a new password to a user account belonging to username:

    ~]# passwd user_name
  • Adding a user to a group:

    ~]# usermod -a -G group_name user_name

For detailed information on managing users and groups, see Chapter 4, Managing Users and Groups.

If you want to use graphical user interface to manage users and groups, see Section 4.2, “Managing Users in a Graphical Environment”.

1.7.2. Managing User Accounts in Cockpit

To manage accounts in Cockpit, select the Accounts menu.

Figure 1.4. Managing User Accounts in Cockpit

Accounts n

1.8. Dumping the Crashed Kernel Using the kdump Mechanism

This section provides an introduction to the Kernel crash dump mechanism, also called kdump, and briefly explains what kdump is used for in Section 1.8.1, “What kdump Is and Which Tasks It Can Be Used For”.

Activation of the kdump service is a part of the installation process, and by default, kdump was enabled during the installation. This section summarizes how to activate kdump during the installation in Section 1.8.2, “Enabling and Activating kdump During the Installation Process”, and how to manually enable the kdump service if it is disabled after the installation in Section 1.8.3, “Ensuring That kdump Is Installed and Enabled after the Installation Process”.

You can also use Cockpit to configure kdump. See Section 1.8.4, “Configuring kdump in Cockpit” for more information.

1.8.1. What kdump Is and Which Tasks It Can Be Used For

In case of a system crash, you can use the Kernel crash dump mechanism called kdump that enables you to save the content of the system’s memory for later analysis. The kdump mechanism relies on the kexec system call, which can be used to boot a Linux kernel from the context of another kernel, bypass BIOS, and preserve the contents of the first kernel’s memory that would otherwise be lost.

When kernel crash occurs, kdump uses kexec to boot into a second kernel (a capture kernel), which resides in a reserved part of the system memory that is inaccessible to the first kernel. The second kernel captures the contents of the crashed kernel’s memory (a crash dump) and saves it.

1.8.2. Enabling and Activating kdump During the Installation Process

During the installation, enablement and activation of kdump can be done either in the Anaconda installer or using the %addon com_redhat_kdump command in the Kickstart file.

For more information, see the appropriate source according to the installation method:

1.8.3. Ensuring That kdump Is Installed and Enabled after the Installation Process

To ensure that kdump is installed and to configure it:

Checking Whether kdump Is Installed and Configuring kdump

  1. To check whether kdump is installed on your system:

    ~]$ rpm -q kexec-tools
  2. If not installed, to install kdump, enter as the root user:

    ~]# yum install kexec-tools
  3. To configure kdump:

    Use either the command line or graphical user interface.

    Both options are described in detail in Red Hat Enterprise Linux 7 Kernel Crash Dump Guide.

    If you need to install the graphical configuration tool:

    ~]# yum install system-config-kdump

1.8.4. Configuring kdump in Cockpit

In Cockpit, select Kernel dump configuration to verify:

  • the kdump status
  • the amount of memory reserved for kdump
  • the location of the crash dump files

Figure 1.5. Configuring kdump in Cockpit

kdump n

1.8.5. Additional Resources on kdump

For more information on kdump, see Red Hat Enterprise Linux 7 Kernel Crash Dump Guide.

1.9. Performing System Rescue and Creating System Backup with ReaR

When a software or hardware failure breaks the operating system, you need a mechanism to rescue the system. It is also useful to have the system backup saved. Red Hat recommends using the Relax-and-Recover (ReaR) tool to fulfil both these needs.

1.9.1. What ReaR Is and Which Tasks It Can Be Used For

ReaR is a disaster recovery and system migration utility which enables you to create the complete rescue system. By default, this rescue system restores only the storage layout and the boot loader, but not the actual user and system files.

Additionally, certain backup software enables you to integrate ReaR for disaster recovery.

ReaR enables to perform the following tasks:

  • Booting a rescue system on the new hardware
  • Replicating the original storage layout
  • Restoring user and system files

1.9.2. Quickstart to Installation and Configuration of ReaR

To install ReaR, enter as the root user:

~]# yum install rear genisoimage syslinux

Use the settings in the /etc/rear/local.conf file to configure ReaR.

For further information see, Section 27.1, “Basic ReaR Usage”.

1.9.3. Quickstart to Creation of the Rescue System with ReaR

To create the rescue system, perform the following command as the root user
~]# rear mkrescue

For further information on creating the rescue system with ReaR, see Section 27.1.3, “Creating a Rescue System”.

1.9.4. Quickstart to Configuration of ReaR with the Backup Software

ReaR contains a fully-integrated built-in, or internal, backup method called NETFS.

To make ReaR use its internal backup method, add these lines to the /etc/rear/local.conf file:

BACKUP=NETFS
BACKUP_URL=backup location

You can also configure ReaR to keep the previous backup archives when the new ones are created by adding the following line to /etc/rear/local.conf:

NETFS_KEEP_OLD_BACKUP_COPY=y

To make the backups incremental, meaning that only the changed files are backed up on each run, add this line to /etc/rear/local.conf:

BACKUP_TYPE=incremental

For detailed information about using the ReaR NETFS internal backup method, see Section 27.2.1, “The Built-in Backup Method”.

For information on supported external backup methods and unsupported backup methods, see Section 27.2.2, “Supported Backup Methods” and Section 27.2.3, “Unsupported Backup Methods”.

1.10. Using the Log Files to Troubleshoot Problems

When troubleshooting a problem, you may appreciate the log files that contain different information and messages about the operating system. The logging system in Red Hat Enterprise Linux 7 is based on the built-in syslog protocol. Particular programs use this system to record events and organize them into log files, which are useful when auditing the operating system and troubleshooting various problems.

For more information on log files, see Chapter 23, Viewing and Managing Log Files.

1.10.1. Services Handling the syslog Messages

The syslog messages are handled by two services:

  • the systemd-journald daemon - Collects messages from the kernel, the early stages of the boot process, standard output and error of daemons as they start up and run, and syslog, and forwards the messages to the rsyslog service for further processing.
  • the rsyslog service - Sorts the syslog messages by type and priority, and writes them to the files in the /var/log directory, where the logs are persistently stored.

1.10.2. Subdirectories Storing the syslog Messages

The syslog messages are stored in various subdirectories under the /var/log directory according to what kind of messages and logs they contain:

  • var/log/messages - all syslog messages except those mentioned below
  • var/log/secure - security and authentication-related messages and errors
  • var/log/maillog - mail server-related messages and errors
  • var/log/cron - log files related to periodically executed tasks
  • var/log/boot.log - log files related to system startup

1.11. Accessing Red Hat Support

To obtain support from Red Hat, use the Red Hat Customer Portal, which provides access to everything available with your subscription.

This section describes:

1.11.1. Obtaining Red Hat Support Through Red Hat Customer Portal

By using the Red Hat Customer Portal you can:

  • Open a new support case
  • Initiate a live chat with a Red Hat expert
  • Contact a Red Hat expert by making a call or sending an email

To access the Red Hat Customer Portal, go to https://access.redhat.com..

To work with Red Hat Customer Portal services related to Red Hat support, you can use:

  • Web browser
  • Red Hat Support Tool

1.11.1.1. What the Red Hat Support Tool Is and Which Tasks It Can Be Used For

The Red Hat Support Tool is a command-line based tool which provides a text console interface to the subscription-based Red Hat access services. This tool is contained in the redhat-support-tool package.

The Red Hat Support Tool enables you to perform support-related tasks, such as:

  • Opening or updating support cases
  • Searching in the Red Hat knowledge base solutions
  • Analyzing Python and Java errors

To start the tool in interactive mode:

~]$ redhat-support-tool
Welcome to the Red Hat Support Tool.
Command (? for help):

In interactive mode, enter ? to display the available commands:

Command (? for help): ?

For more information about the installation and use of the Red Hat Support Tool, see Chapter 8, Accessing Support Using the Red Hat Support Tool, and the Red Hat Knowledgebase article Red Hat Access: Red Hat Support Tool.

1.11.2. Using the SOS Report to Troubleshoot Problems

The SOS report collects configuration details, system information and diagnostic information from a Red Hat Enterprise Linux system. Attach the report when you open a support case.

Note that the SOS report is provided in the sos package, which is not installed with the default minimal installation of Red Hat Enterprise Linux 7.

To install the sos package:

~]# yum install sos

To generate an SOS report:

~]# sosreport

To attach the sos report to your support case, see the Red Hat Knowledgebase article How can I attach a file to a Red Hat support case?. Note that you will be prompted to enter the number of the support case, when attaching the sos report.

For more information on SOS report, see the Red Hat Knowledgebase article What is a sosreport and how to create one in Red Hat Enterprise Linux 4.6 and later?.