Chapter 10. Managing system upgrades with snapshots

Procedure

1. Create a snapshot of your root logical volume:

   • If your root file system uses thin provisioning, create a thin snapshot:

     # lvcreate -s rhel/root -kn -n root_snapshot_before_changes
      Logical volume "root_snapshot_before_changes" created.

     Here:

     • -s creates the snapshot.
     • rhel/root copies the file system to the logical volume.
     • -kn automatically activates LV at boot time.

     • -n root_snapshot_before_changes shows the name of the snapshot.

       While creating a thin snapshot, do not define the snapshot size. The snapshot is allocated from the thin pool.

   • If your root file system uses thick provisioning, create a thick snapshot:

     # lvcreate -s rhel/root -n root_snapshot_before_changes -L 25g
       Rounding up size to full physical extent 25 GiB
       Logical volume "root_snapshot_before_changes" created.

     In this command:

     • -s creates the snapshot.
     • rhel/root copies the file system to the logical volume.
     • -n root_snapshot_before_changes shows the name of the snapshot.

     • -L 25g is the snapshot size. Make a size estimate based on the size of the original installation.

       While creating a thick snapshot, define the snapshot size that can hold all the changes during the upgrade.

       Important

       The created snapshot does not include any additional system changes.

2. Create the profile:

   Creating a profile requires an architecture-specific workaround to avoid an interaction between kexec-tools or kdumpctl and boom. During the upgrade, the updated kexec-tools package attempts to modify all boot entries with updated crashkernel settings. This deletes the boot images used by the entry. You can avoid this by appending the RHEL 9 crashkernel settings to the RHEL 8 profile options.

   • On an Intel 64 or AMD64 (x86_64), or IBM Z (s390x) architecture:

     # boom profile create --from-host --os-options "root=%{root_device} ro %{root_opts} rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M"
     Created profile with os_id 43747d3:
       OS ID: "43747d3888b663d2bc88efd35d0813159a84d291",
       Name: "Red Hat Enterprise Linux", Short name: "rhel",
       Version: "8.9 (Ootpa)", Version ID: "8.9",
       Kernel pattern: "/vmlinuz-%{version}", Initramfs pattern: "/initramfs-%{version}.img",
       Root options (LVM2): "rd.lvm.lv=%{lvm_root_lv}",
       Root options (BTRFS): "rootflags=%{btrfs_subvolume}",
       Options: "root=%{root_device} ro %{root_opts} rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M",
       Title: "%{os_name} %{os_version_id} (%{version})",
       Optional keys: "", UTS release pattern: "el8"

   • On an 64-bit ARM (AArch64) architecture:

     # boom profile create --from-host --os-options "root=%{root_device} ro %{root_opts} rhgb quiet crashkernel=1G-4G:256M,4G-64G:320M,64G-:576M"

   • On an IBM POWER little-endian (ppc64le) architecture:

     # boom profile create --from-host --os-options "root=%{root_device} ro %{root_opts} rhgb quiet crashkernel=2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G" --optional-keys "grub_users grub_arg grub_class id"

     The --optional-keys argument is required on ppc64le to ensure that the grub2-mkconfig command generates the correct boot entry in step 10.2.3. For more information, see RHEL-36180.

3. Create a snapshot boot entry of the original system using backup copies of the original boot images:

   # boom create --backup --title "Root LV snapshot before changes" --rootlv rhel/root_snapshot_before_changes
   WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
   Created entry with boot_id c919f89:
     title Root LV snapshot before changes
     machine-id b1dcec73886b45218892b1a7bbfa0dee
     version 4.18.0-513.24.1.el8_9.x86_64
     linux /vmlinuz-4.18.0-513.24.1.el8_9.x86_64.boom0
     initrd /initramfs-4.18.0-513.24.1.el8_9.x86_64.img.boom0
     options root=/dev/rhel/root_snapshot_before_changes ro rd.lvm.lv=rhel/root_snapshot_before_changes rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M

   Here:

   • --title "Root LV snapshot before changes" is the name of the boot entry, that shows in the boot entry list during system startup.

   • --rootlv is the root logical volume that corresponds to the new boot entry.

     After you complete the previous step, you have a boot entry that enables access to the original system, before the upgrade.

     Ignore "WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'". For details, see RHEL-35983.

   • On systems with ppc64le architecture, update boot entries:

     # grub2-mkconfig -o /boot/grub2/grub.cfg
     Generating grub configuration file ...
     Generating boot entries from BLS files...
     done

4. Upgrade to Red Hat Enterprise Linux 9 using the Leapp utility:

   # leapp upgrade
   ==> Processing phase `configuration_phase`
   ====> * ipu_workflow_config
           IPU workflow config actor
   ==> Processing phase `FactsCollection`
   ...
   ============================================================
                         REPORT OVERVIEW
   ============================================================
   
   Upgrade has been inhibited due to the following problems:
       1. Firewalld Configuration AllowZoneDrifting Is Unsupported
       2. Possible problems with remote login using root account
   
   HIGH and MEDIUM severity reports:
       1. Remote root logins globally allowed using password
       2. GRUB2 core will be automatically updated during the upgrade
   
   Reports summary:
       Errors:                      0
       Inhibitors:                  2
       HIGH severity reports:       2
       MEDIUM severity reports:     0
       LOW severity reports:        1
       INFO severity reports:       3
   
   Before continuing consult the full report:
       A report has been generated at /var/log/leapp/leapp-report.json
       A report has been generated at /var/log/leapp/leapp-report.txt
   
   ============================================================
                      END OF REPORT OVERVIEW
   ============================================================

   Review and resolve any blockers indicated by the leapp upgrade command report. For detailed instructions on the report, see Reviewing the pre-upgrade report.

5. Reboot into the upgrade boot entry:

   # leapp upgrade --reboot
   ==> Processing phase `configuration_phase`
   ====> * ipu_workflow_config
           IPU workflow config actor
   ==> Processing phase `FactsCollection`
   ...

   Select the Red Hat Enterprise Linux Upgrade Initramfs entry from the GRUB boot screen.

   Note

   The Snapshots submenu from the GRUB boot screen is not available in Red Hat Enterprise Linux 9.

Procedure

1. Reboot the system:

   # reboot

2. Select the required boot entry from the GRUB boot loader screen.

Procedure

1. Boot into Red Hat Enterprise Linux 9 from the GRUB boot loader screen.

2. After the system loads, view the available boot entries. The following output shows the snapshot boot entry in the list of boom boot entries:

   # boom list
   BootID  Version                      Name                     RootDevice
   1e1a9b4 4.18.0-513.5.1.el8_9.x86_64  Red Hat Enterprise Linux /dev/mapper/rhel-root
   4ea37b9 4.18.0-513.24.1.el8_9.x86_64 Red Hat Enterprise Linux /dev/mapper/rhel-root
   c919f89 4.18.0-513.24.1.el8_9.x86_64 Red Hat Enterprise Linux /dev/rhel/root_snapshot_before_changes

3. Delete the snapshot entry by using the BootID value:

   # boom delete --boot-id c919f89
   Deleted 1 entry

   This deletes the boot entry from the GRUB menu.

4. Remove the LV snapshot:

   # lvremove rhel/root_snapshot_before_changes
   Do you really want to remove active logical volume rhel/root_snapshot_before_changes? [y/n]: y
         Logical volume "root_snapshot_before_changes" successfully removed

5. Complete the remaining post-upgrade tasks. For details, see Upgrading from RHEL 8 to RHEL 9.

Procedure

1. Merge the snapshot with the original volume:

   # lvconvert --merge rhel/root_snapshot_before_changes
     Logical volume rhel/root_snapshot_before_changes contains a filesystem in use.
     Delaying merge since snapshot is open.
     Merging of thin snapshot rhel/root_snapshot_before_changes will occur on next activation of rhel/root.

   Warning

   After you merge the snapshot, you must continue with all the remaining steps in this procedure to prevent data loss.

2. Create a rollback boot entry for the merged snapshot:

   # boom create --backup --title "RHEL Rollback" --rootlv rhel/root
   WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
   WARNING - Options for BootEntry(boot_id=1e1a9b4) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=1ccc554) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=4ea37b9) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=e22dd61) do not match OsProfile: marking read-only
   Created entry with boot_id 6c44638:
     title RHEL Rollback
     machine-id b1dcec73886b45218892b1a7bbfa0dee
     version 4.18.0-513.24.1.el8_9.x86_64
     linux /vmlinuz-4.18.0-513.24.1.el8_9.x86_64.boom0
     initrd /initramfs-4.18.0-513.24.1.el8_9.x86_64.img.boom0
     options root=/dev/rhel/root ro rd.lvm.lv=rhel/root rhgb quiet crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M

   Ignore all WARNING messages, see RHEL-35983.

3. Reboot your machine to restore the operating system state:

   # reboot

   • After the system reboots, select the RHEL Rollback boot entry from the GRUB screen.

   • When the root logical volume is active, the system automatically starts the snapshot merge operation.

     Important

     When the merge operation starts, the snapshot volume is no longer available. After successfully booting the RHEL Rollback boot entry, the Root LV snapshot boot entry no longer works. Merging the snapshot logical volume destroys the Root LV snapshot and restores the prior state of the original volume.

4. After you complete the merge operation, remove the unused entries and restore the original boot entry:

   1. Remove the unused Red Hat Enterprise Linux 9 boot entries from the /boot file system and rebuild the grub.cfg file for the changes to take effect:

      # rm -f /boot/loader/entries/*.el9*

      # rm -f /boot/*.el9*

      # grub2-mkconfig -o /boot/grub2/grub.cfg
      Generating grub configuration file ...
      done

5. After a successful rollback to the system, delete the boom snapshot and rollback boot entries:

   # boom list -o+title
   WARNING - Options for BootEntry(boot_id=1e1a9b4) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=1ccc554) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=4ea37b9) do not match OsProfile: marking read-only
   BootID  Version                      Name                     RootDevice                             Title
   1e1a9b4 4.18.0-513.5.1.el8_9.x86_64  Red Hat Enterprise Linux /dev/mapper/rhel-root                  Red Hat Enterprise Linux (4.18.0-513.5.1.el8_9.x86_64) 8.9 (Ootpa)
   4ea37b9 4.18.0-513.24.1.el8_9.x86_64 Red Hat Enterprise Linux /dev/mapper/rhel-root                  Red Hat Enterprise Linux (4.18.0-513.24.1.el8_9.x86_64) 8.9 (Ootpa)
   c919f89 4.18.0-513.24.1.el8_9.x86_64 Red Hat Enterprise Linux /dev/rhel/root_snapshot_before_changes Root LV snapshot before changes
   6c44638 4.18.0-513.24.1.el8_9.x86_64 Red Hat Enterprise Linux /dev/rhel/root                         RHEL Rollback

   # boom delete c919f89
   WARNING - Options for BootEntry(boot_id=1e1a9b4) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=1ccc554) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=4ea37b9) do not match OsProfile: marking read-only
   Deleted 1 entry

   # boom delete 6c44638
   WARNING - Options for BootEntry(boot_id=1e1a9b4) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=1ccc554) do not match OsProfile: marking read-only
   WARNING - Options for BootEntry(boot_id=4ea37b9) do not match OsProfile: marking read-only
   Deleted 1 entry

   Ignore the warnings. For details, see RHEL-35983.