Chapter 16. Renaming IdM client systems

The following sections describe how to change the host name of an Identity Management (IdM) client system.

Warning

Renaming a client is a manual procedure. Do not perform it unless changing the host name is absolutely required.

Renaming an IdM client involves:

  1. Preparing the host. For details, see Preparing an IdM client for its renaming.
  2. Uninstalling the IdM client from the host. For details, see Uninstalling a client.
  3. Renaming the host. For details, see Renaming a client.
  4. Installing the IdM client on the host with the new name. For details, see Reinstalling a client.
  5. Configuring the host after the IdM client installation. For details, see Re-adding services, re-generating certificates, and re-adding host groups.

16.1. Preparing an IdM client for its renaming

Before uninstalling the current client, make note of certain settings for the client. You will apply this configuration after re-enrolling the machine with a new host name.

  • Identify which services are running on the machine:

    • Use the ipa service-find command, and identify services with certificates in the output:

      $ ipa service-find old-client-name.example.com
    • In addition, each host has a default host service which does not appear in the ipa service-find output. The service principal for the host service, also called a host principal, is host/old-client-name.example.com.
  • For all service principals displayed by ipa service-find old-client-name.example.com, determine the location of the corresponding keytabs on the old-client-name.example.com system:

    # find / -name "*.keytab"

    Each service on the client system has a Kerberos principal in the form service_name/host_name@REALM, such as ldap/old-client-name.example.com@EXAMPLE.COM.

  • Identify all host groups to which the machine belongs.

    # ipa hostgroup-find old-client-name.example.com

16.2. Uninstalling an IdM client

Uninstalling a client removes the client from the Identity Management (IdM) domain, along with all of the specific IdM configuration of system services, such as System Security Services Daemon (SSSD). This restores the previous configuration of the client system.

Procedure

  1. Enter the ipa-client-install --uninstall command:

    [root@client ~]# ipa-client-install --uninstall
  2. Optional: Check that you cannot obtain a Kerberos ticket-granting ticket (TGT) for an IdM user:

    [root@client ~]# kinit admin
    kinit: Client 'admin@EXAMPLE.COM' not found in Kerberos database while getting initial credentials
    [root@client ~]#

    If a Kerberos TGT ticket has been returned successfully, follow the additional uninstallation steps in Uninstalling an IdM client: additional steps after multiple past installations.

  3. On the client, remove old Kerberos principals from each identified keytab other than /etc/krb5.keytab:

    [root@client ~]# ipa-rmkeytab -k /path/to/keytab -r EXAMPLE.COM
  4. On an IdM server, remove all DNS entries for the client host from IdM:

    [root@server ~]# ipa dnsrecord-del
    Record name: old-client-name
    Zone name: idm.example.com
    No option to delete specific record provided.
    Delete all? Yes/No (default No): yes
    ------------------------
    Deleted record "old-client-name"
  5. On the IdM server, remove the client host entry from the IdM LDAP server. This removes all services and revokes all certificates issued for that host:

    [root@server ~]# ipa host-del client.idm.example.com
    Important

    Removing the client host entry from the IdM LDAP server is crucial if you think you might re-enroll the client in the future, with a different IP address or a different hostname.

16.3. Uninstalling an IdM client: additional steps after multiple past installations

If you install and uninstall a host as an Identity Management (IdM) client multiple times, the uninstallation procedure might not restore the pre-IdM Kerberos configuration.

In this situation, you must manually remove the IdM Kerberos configuration. In extreme cases, you must reinstall the operating system.

Prerequisites

  • You have used the ipa-client-install --uninstall command to uninstall the IdM client configuration from the host. However, you can still obtain a Kerberos ticket-granting ticket (TGT) for an IdM user from the IdM server.
  • You have checked that the /var/lib/ipa-client/sysrestore directory is empty and hence you cannot restore the prior-to-IdM-client configuration of the system using the files in the directory.

Procedure

  1. Check the /etc/krb5.conf.ipa file:

    • If the contents of the /etc/krb5.conf.ipa file are the same as the contents of the krb5.conf file prior to the installation of the IdM client, you can:

      1. Remove the /etc/krb5.conf file:

        # rm /etc/krb5.conf
      2. Rename the /etc/krb5.conf.ipa file into /etc/krb5.conf:

        # mv /etc/krb5.conf.ipa /etc/krb5.conf
    • If the contents of the /etc/krb5.conf.ipa file are not the same as the contents of the krb5.conf file prior to the installation of the IdM client, you can at least restore the Kerberos configuration to the state directly after the installation of the operating system:
    1. Re-install the krb5-libs package:

      # yum reinstall krb5-libs

      As a dependency, this command will also re-install the krb5-workstation package and the original version of the /etc/krb5.conf file.

  2. Remove the var/log/ipaclient-install.log file if present.

Verification steps

  • Try to obtain IdM user credentials. This should fail:

    [root@r8server ~]# kinit admin
    kinit: Client 'admin@EXAMPLE.COM' not found in Kerberos database while getting initial credentials
    [root@r8server ~]#

The /etc/krb5.conf file is now restored to its factory state. As a result, you cannot obtain a Kerberos TGT for an IdM user on the host.

16.4. Renaming the host system

Rename the machine as required. For example:

# hostnamectl set-hostname new-client-name.example.com

You can now re-install the Identity Management (IdM) client to the IdM domain with the new host name.

16.5. Re-installing an IdM client

Install an client on your renamed host following the procedure described in Installing a client.

16.6. Re-adding services, re-generating certificates, and re-adding host groups

  1. On the Identity Management (IdM) server, add a new keytab for every service identified in the Preparing an IdM client for its renaming.

    [root@server ~]# ipa service-add service_name/new-client-name
  2. Generate certificates for services that had a certificate assigned in the Preparing an IdM client for its renaming. You can do this:

    • Using the IdM administration tools
    • Using the certmonger utility
  3. Re-add the client to the host groups identified in the Preparing an IdM client for its renaming.