How to Migrate CentOS 7 to AlmaLinux 8: A Step-by-Step Guide

It’s now easier than ever to migrate from CentOS 7 to AlmaLinux 8, thanks to the AlmaLinux project called ELevate. Here's how to do it!

In the ever-evolving landscape of Linux distributions, CentOS has long been a popular choice for its stability, reliability, and long-term support.

However, with the unexpected shift in CentOS’s strategy to focus on CentOS Stream, many users have found themselves seeking an alternative solution.

So, have you ever asked yourself: How do I migrate from CentOS 7 to AlmaLinux? You don’t need to worry about this anymore because this step-by-step guide will walk you through migrating your CentOS 7 installation to AlmaLinux 8, ensuring a smooth and hassle-free transition.

So far, so good, but how to do it? For those unaware, the AlmaLinux ELevate project allows users to upgrade or migrate between any RHEL-based distro. So let’s dive in and do it.

Here is our CentOS 7 system before starting the migration process to AlmaLinux 8.

CentOS 7 system before migration to AlmaLinux 8

1. Take System Backup

Before upgrading, please back up all your essential data and take a snapshot of the complete CentOS 7 system. This way, you will be on the right side if anything goes wrong.

Alternatively, you can always use a command like the one below to archive all the more important directories and their contents in a single tar.gz archive file.

sudo tar czf /centos7.tar.gz \
     --exclude=/centos7.tar.gz \
     --exclude=/dev \
     --exclude=/mnt \
     --exclude=/proc \
     --exclude=/sys \
     --exclude=/run \
     --exclude=/tmp \
     --exclude=/media \
     --exclude=/lost+found \
     /

Of course, add more “–exclude=” parameters if you need to. Finally, the command creates a backup of all the files and directories by placing them in the centos7.tar.gz archive in the root (/) partition.

Then, this file must be transferred to another computer or drive, for example, with the help of the SCP command.

2. Upgrade the Current CentOS 7 System

The next step in the upgrade process is to ensure we have a wholly upgraded system. Update existing software with the following command:

sudo yum update

Once all the packages are updated, reboot your system to apply the changes.

Now let’s verify our current operating system version.

cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)

As you can see, the system runs CentOS 7.9, the latest CentOS version in the 7.x branch.

3. Migrate CentOS 7 to AlmaLinux 8

3.1 Install ELevate

The first step in the upgrade process is installing the “elevate-release” package on your current CentOS 7 system.

sudo yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el7.noarch.rpm
Installing the elevate-release package

3.2 Install Leapp and Migration Data

The migration process is based on using Red Hat’s Leapp utility. It combines Red Hat’s Leapp framework with a community-created library and service for its required migration metadata set.

Therefore the next step is to install the required packages, which in our case, we wish to upgrade from CentOS 7 to AlmaLinux 8.

sudo yum install -y leapp-upgrade leapp-data-almalinux

3.3 Start a Pre-upgrade Check

The next step is to start a pre-upgrade check. The below command verifies server compatibility without any actual changes:

sudo leapp preupgrade

Probably the check will fail, but don’t panic! That’s normal because some tweaks are required in advance.

CentOS 7 to AlmaLinux 8 migration -Preupgrade check

According to the official documentation, those three commands are shown below to solve the problem. Just run them one after the other:

sudo rmmod pata_acpi
echo PermitRootLogin yes | sudo tee -a /etc/ssh/sshd_config
sudo leapp answer --section remove_pam_pkcs11_module_check.confirm=True

(Optional) If you rerun the check, the pre-upgrade check will succeed.

sudo leapp preupgrade
CentOS 7 to AlmaLinux 8 migration -Preupgrade check succeeded

3.4 Start the Upgrade Process from CentOS 7 to AlmaLinux 8

Now you can run the following command to migrate CentOS 7 to AlmaLinux 8.

sudo leapp upgrade

Be patient since the upgrade process could take some time. Once the migration is completed, you’ll be offered to reboot the system:

sudo reboot

A new entry in GRUB called ELevate-Upgrade-Initramfs will appear. Hit Enter and wait for the upgrade process to finish. The system will be automatically booted into it. 

ELevate Upgrade Initramfs

And you will be welcomed by the AlmaLinux 8 GRUB menu at boot time.

Alma Linux 8 Boot Menu

4. Check the OS Version

To confirm that you have successfully migrated from CentOS 7 to AlmaLinux 8, check the OS version:

cat /etc/redhat-release
AlmaLinux release 8.4 (Electric Cheetah)

That’s all. Congratulations! You have successfully migrated to AlmaLinux 8.

(Optional) In addition, you can update the server hostname to match with AlmaLinux.

sudo hostnamectl set-hostname almalinux8
sudo reboot
CentOS 7 to AlmaLinux 8: Migration succeeded

Conclusion

AlmaLinux’s ELevate tool is a great one! It may be a fantastic option if you want to migrate from CentOS 7 to AlmaLinux 8.

In addition, if you are running CentOS 8.x, all you have to do to switch to AlmaLinux 8 is follow our CentOS 8 to AlmaLinux 8: A Step-by-Step Migration Guide.

I have made this guide as simple as possible. Thanks for using it! Feel free to share your thoughts in the comments box below.

Bobby Borisov

Bobby Borisov

Bobby, an editor-in-chief at Linuxiac, is a Linux professional with over 20 years of experience. With a strong focus on Linux and open-source software, he has worked as a Senior Linux System Administrator, Software Developer, and DevOps Engineer for small and large multinational companies.

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13 Comments

  1. Hello,
    I tried the upgrade on CentOS 7.9, it froze on libvirtio (I’m writing from memory, it resembled something like that), then forced a reboot and now grub shows the old menu, Alma Linux tries to start, shows a lot of errors, then the cursor flashes and nothing else happens.
    I have no clue what to do from here! That server is now down, the upgrade failed.

  2. After solving the “inhibitors”, I always get the following error…

    ============================================================
    ERRORS
    ============================================================

    2022-05-14 15:14:39.704179 [ERROR] Actor: target_userspace_creator
    Message: Unable to install RHEL 8 userspace packages.
    Summary:
    Details: Command [‘systemd-nspawn’, ‘–register=no’, ‘–quiet’, ‘-D’, ‘/var/lib/leapp/scratch/mounts/root_/system_overlay’, ‘–setenv=LEAPP_NO_RHSM=0’, ‘–setenv=LEAPP_EXPERIMENTAL=0’, ‘–setenv=LEAPP_COMMON_TOOLS=:/etc/leapp/repos.d/system_upgrade/el7toel8/tools’, ‘–setenv=LEAPP_COMMON_FILES=:/etc/leapp/repos.d/system_upgrade/common/files:/etc/leapp/repos.d/system_upgrade/el7toel8/files’, ‘–setenv=LEAPP_UNSUPPORTED=0’, ‘–setenv=LEAPP_EXECUTION_ID=d5278bb5-e873-438d-b094-c7e1ebfcc069’, ‘–setenv=LEAPP_HOSTNAME=srv-net-072.alpaca.int’, ‘dnf’, ‘install’, ‘-y’, ‘–nogpgcheck’, ‘–setopt=module_platform_id=platform:el8’, ‘–setopt=keepcache=1’, ‘–releasever’, u’8.4′, ‘–installroot’, ‘/el8target’, ‘–disablerepo’, ‘*’, ‘–enablerepo’, u’almalinux8-baseos’, ‘–enablerepo’, u’almalinux8-powertools’, ‘–enablerepo’, u’almalinux8-resilientstorage’, ‘–enablerepo’, u’almalinux8-extras’, ‘–enablerepo’, u’almalinux8-highavailability’, ‘–enablerepo’, u’almalinux8-appstream’, ‘dnf’, ‘dnf-command(config-manager)’, ‘–disableplugin’, ‘subscription-manager’] failed with exit code 1.
    Stderr: Failed to create directory /var/lib/leapp/scratch/mounts/root_/system_overlay//sys/fs/selinux: Read-only file system
    Failed to create directory /var/lib/leapp/scratch/mounts/root_/system_overlay//sys/fs/selinux: Read-only file system
    Host and machine ids are equal (4e3bf1688a5744d698d980f621bf9021): refusing to link journals
    Failed to synchronize cache for repo ‘almalinux8-highavailability’, ignoring this repo.
    Failed to synchronize cache for repo ‘almalinux8-extras’, ignoring this repo.
    Failed to synchronize cache for repo ‘almalinux8-baseos’, ignoring this repo.
    Failed to synchronize cache for repo ‘almalinux8-appstream’, ignoring this repo.
    Failed to synchronize cache for repo ‘almalinux8-powertools’, ignoring this repo.
    Failed to synchronize cache for repo ‘almalinux8-resilientstorage’, ignoring this repo.
    Error: Unable to find a match: dnf dnf-command(config-manager)

    ============================================================
    END OF ERRORS
    ============================================================

    • Hello ArVie,
      I’m having the same problem here. I’ve tried several ways to overpass it but nothing seems to work.
      Have you found any fix to it?
      tx in advance.

    • Hello ArVie,

      Does your server have a direct access on the net ?

      If not, you may try to replace the file /etc/leapp/files/leapp_upgrade_repositories.repo with URL for your own repo cache.
      It’s my case, and with our own reposerver, this migration is quite easy !

  3. The downloaded packages were saved in cache until the next successful transaction.
    You can remove cached packages by executing ‘dnf clean packages’.
    Process Process-476:
    Traceback (most recent call last):
    File “/usr/lib64/python2.7/multiprocessing/process.py”, line 258, in _bootstrap
    self.run()
    File “/usr/lib64/python2.7/multiprocessing/process.py”, line 114, in run
    self._target(*self._args, **self._kwargs)
    File “/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py”, line 72, in _do_run
    actor_instance.run(*args, **kwargs)
    File “/usr/lib/python2.7/site-packages/leapp/actors/__init__.py”, line 290, in run
    self.process(*args)
    File “/usr/share/leapp-repository/repositories/system_upgrade/common/actors/dnfpackagedownload/actor.py”, line 51, in process
    xfs_info=xfs_info, storage_info=storage_info, plugin_info=plugin_info, on_aws=on_aws
    File “/usr/share/leapp-repository/repositories/system_upgrade/common/libraries/dnfplugin.py”, line 385, in perform_rpm_download
    test=True, on_aws=on_aws
    File “/usr/share/leapp-repository/repositories/system_upgrade/common/libraries/dnfplugin.py”, line 219, in _transaction
    e.stdout = e.stdout.encode(‘utf-8’, ‘xmlcharrefreplace’)
    AttributeError: can’t set attribute

      • turns out it had nothing to do with python but the container overlay image at /var/lib/leapp
        is set to default 2048MB. There wasn’t enough space so i increased it by running
        export LEAPP_OVL_SIZE=4000
        and that fixed it

  4. When I did the yum update, Kernel 3.10.0-1160.80.1.el7.x86_64 was installed. Rebooting on that only goes to line-driven terminal with all kinds of problems (too numerous to convey, but includes things like failure to mount drives, etc). I can successfully reboot into the previous Kernel (3.10.0-1160.76.1.el7.x86_64). I removed the patch 80 copy of the Kernel and rebooted again. Then when I run leapp preupgrade, the report says that I have to be running the latest installed Kernel. I’m stuck in a catch 22. I am not a Linux expert by any means and there are none here. Are there any suggestions?

  5. This is exceptionally well documented. But I can see by various comments that the upgrade is fraught with danger. Any upgrade is very dicey. So I am not sure whether to continue using Centos 7 until it just dies. I am getting more and more RACE warnings.

  6. I was already running the upgrade, i mistakenly pressed the keypad and the installation stopped and since then i cant upgrade anymore, started giving errors, what can i do to start over

  7. Thanks for this guide! It is a precious help and very well explained!

    The only little thing to mention is the server must contact alma repositories directly on the net, or replace URLs in this file /etc/leapp/files/leapp_upgrade_repositories.repo with your own repository servers before launching pre-upgrade and upgrade !

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