Upgrading from RHEL 6 to RHEL 7

Procedure

1. Ensure that your system is registered to Red Hat Subscription Management (RHSM).

   If your RHEL 6 system is registered to Red Hat Network (RHN), you must migrate to RHSM. See Migrating from RHN to RHSM in Red Hat Enterprise Linux for details.

2. Ensure that you have access to the latest RHEL 6 content. If you use the yum-plugin-versionlock plug-in to lock packages to a specific version, clear the lock:

   # yum versionlock clear

   See How to restrict yum to install or upgrade a package to a fixed specific package version? for more information.

3. Enable the Extras repository, which contains necessary packages for a pre-upgrade assessment and an in-place upgrade.

   1. For the Server variant on the 64-bit Intel architecture on server edition:

      # subscription-manager repos --enable rhel-6-server-extras-rpms --enable rhel-6-server-optional-rpms

   2. For IBM POWER, big endian systems:

      # subscription-manager repos --enable rhel-6-for-power-extras-rpms --enable rhel-6-for-power-optional-rpms

   3. For the IBM Z architecture:

      # subscription-manager repos --enable rhel-6-for-system-z-extras-rpms --enable rhel-6-for-system-z-optional-rpms

   4. For the HPC Compute Node variant on the 64-bit Intel architecture:

      # subscription-manager repos --enable rhel-6-for-hpc-node-extras-rpms --enable rhel-6-for-hpc-node-optional-rpms

4. Install the Preupgrade Assistant and Red Hat Upgrade Tool:

   # yum install preupgrade-assistant preupgrade-assistant-el6toel7 redhat-upgrade-tool

   Note

   If your system does not have internet access, you can download the Preupgrade Assistant and Red Hat Upgrade Tool from the Red Hat Customer Portal. For more information, see How to install preupgrade assessment packages on an offline system for RHEL 6.10 to RHEL 7.9 upgrade.

5. Remove all unsupported package groups:

   # yum groupremove group_name

   Replace group_name with each unsupported group name. To locate a list of installed group names, run yum grouplist.

6. Check Known Issues and apply workarounds where applicable. Especially, on systems with multiple network interfaces:

   1. If the system has static routes configured, replace the static route file. See redhat-upgrade-tool fails to reconfigure the static routes on the network interfaces, preventing the upgrade to happen for more information.
   2. If the system runs NetworkManager, stop NetworkManager prior to running the upgrade tool. See redhat-upgrade-tool fails to reconfigure the network interfaces, preventing the upgrade to happen for more information.

7. Update all packages to their latest RHEL 6 version:

   # yum update

8. Reboot the system:

   # reboot

9. Back up all your data before performing the upgrade to prevent potential data loss.

Verification

1. Verify that you are registered with the Red Hat Subscription Manager:

   # yum update

   The Loaded plug-ins: entry must contain subscription-manager.

2. Verify that only supported package groups are installed:

   # yum grouplist

Procedure

1. Prepare source repositories or media with RHEL 7 packages in one of the following locations:

   • An installation repository created from a DVD ISO where you download RHEL 7 packages, for example, an FTP server or an HTTPS site that contains the RHEL 7.9 packages. For more information, see Preparing installation sources.
   • Mounted installation media

   • An ISO image

     In any of the above options, you can configure custom repositories and additional repositories provided by Red Hat. For example, certain packages available in the RHEL 6 Base system are provided in the RHEL 7 Extras repository and are not on a RHEL 7 DVD.

     If you know that your system requires packages that are not in the RHEL 7 Base repository, you can install a separate RHEL 7 system to act as a yum repository that provides the required packages over FTP or HTTP.

     To set up an additional repository that you can use during the upgrade, follow instructions in How to create a local repository for updates. Then use the --addrepo=REPOID=URL option with the redhat-upgrade-tool command.

     Important

     It is strongly recommended to use RHEL 7.9 GA source repositories to prevent booting issues after the upgrade. For more information, see Known Issues.

2. Disable active repositories to prevent problems with combining packages from different major releases of RHEL.

   1. Install the yum-utils package:

      # yum install yum-utils

   2. Disable active repositories:

      # yum-config-manager --disable \*

      For more information, see Can I install packages from different versions of RHEL.

3. Run the Red Hat Upgrade Tool to download RHEL 7 packages and prepare the package installation. Specify the location of the Red Hat Enterprise Linux 7 packages:

   • Installation repository

     # redhat-upgrade-tool --network 7.9 --instrepo ftp-or-http-url --cleanup-post

   • Mounted installation media

     # redhat-upgrade-tool --device device_path --cleanup-post

     If you do not specify the device path, the Red Hat Upgrade Tool scans all mounted removable devices.

   • ISO image

     # redhat-upgrade-tool --iso iso_path --cleanup-post

     Important

     You can use the following options with the redhat-upgrade-tool command for all three locations:

     • --cleanup post: Automatically removes Red Hat-signed packages that do not have a RHEL 7 replacement. Recommended. If you do not use the --cleanup-post option, you must remove all remaining RHEL 6 packages after the in-place upgrade to ensure that your system is fully supported.
     • --snapshot-root-lv and --snapshot-lv: Creates snapshots of system volumes. Snapshots are required to perform a rollback of the RHEL system in case of upgrade failure. For more information, see Rollbacks and cleanup after upgrading RHEL 6 to RHEL 7.

4. Reboot the system when prompted.

   # reboot

   Depending on the number of packages being upgraded, this process can take up to several hours to complete.

5. Manually perform any post-upgrade tasks described in the pre-upgrade assessment result.
6. If your system architecture is 64-bit Intel, upgrade from GRUB Legacy to GRUB 2. See the System Administrators Guide for more information.
7. If Samba is installed on the upgraded host, manually run the testparm utility to verify the /etc/samba/smb.conf file. If the utility reports any configuration errors, you must fix them before you can start Samba.

8. Optional: If you did not use the --cleanup-post option when running the Red Hat Upgrade Tool, clean up orphaned RHEL 6 packages:

   # rpm -qa | grep .el6 &> /tmp/el6.txt
   # rpm -e $(cat /tmp/el6.txt) --nodeps

   Warning

   Be careful not to accidentally remove custom packages that are compatible with RHEL 7.

   Warning

   Using the rpm command to remove orphaned packages might cause broken dependencies in some RHEL 7 packages. Refer to Fixing dependency errors for information about how to fix those dependency errors.

9. Update your new RHEL 7 packages to their latest version.

   # yum update
   # reboot

Verification

1. Verify that the system was upgraded to the latest version of RHEL 7.

   # cat /etc/redhat-release
   Red Hat Enterprise Linux Server release 7.9 (Maipo)

2. Verify that the system is automatically resubscribed for RHEL 7.

   # yum repolist
   Loaded plugins: product-id, subscription-manager
   repo id                             repo name                                  status
   rhel-7-server-rpms/7Server/x86_64   Red Hat Enterprise Linux 7 Server (RPMs)   23,676

   If the repository list does not contain RHEL repositories, run the following commands to unsubscribe the system, resubscribe the system as a RHEL 7 system, and add required repositories:

   # subscription-manager remove --all
   # subscription-manager unregister
   # subscription-manager register
   # subscription-manager attach --pool=poolID
   # subscription-manager repos --enable=repoID