AlmaLinux8

Version 1: Starting template for moving away from CentOS8 due to its end of life. AlmaLinux provides a direct, binary-compatible substitute for CentOS8.

Migration guidance for those looking to upgrade or transfer their CentOS8 templates

The following is drawn from AlmaLinux's official documentation, available at https://github.com/AlmaLinux/almalinux-deploy. We recommend checking that link for the most current version; the text here is a snapshot from March 29, 2022, included for reference. This is offered as a resource for our community, but we assume no liability for any mistakes or issues that might arise from its use.

almalinux-deploy

A migration utility to convert an EL system over to AlmaLinux.

Usage

To convert your EL8 OS to AlmaLinux, take these steps:

CentOS 8.4 or 8.5 is needed to switch to AlmaLinux. While moving to 8.5 before the conversion is advised, it's not strictly required if you're already on at least 8.4. A restart after applying any new updates is suggested.
```
sudo dnf update -y
sudo reboot
```

Since January 31, 2022, the CentOS 8 mirrorlists have been unavailable. To run dnf update -y without issues, you'll need to adjust your dnf configuration to point to a working mirror. The following sed commands offer a convenient way to bring dnf back to a functional state, allowing you to update to 8.5 and then migrate to AlmaLinux.

sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[baseos\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/BaseOS/$basearch/os' /etc/yum.repos.d/CentOS-Linux-BaseOS.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[appstream\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/AppStream/$basearch/os' /etc/yum.repos.d/CentOS-Linux-AppStream.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[cr\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/ContinuousRelease/$basearch/os' /etc/yum.repos.d/CentOS-Linux-ContinuousRelease.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[devel\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/Devel/$basearch/os' /etc/yum.repos.d/CentOS-Linux-Devel.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[extras\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/extras/$basearch/os' /etc/yum.repos.d/CentOS-Linux-Extras.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[fasttrack\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/fasttrack/$basearch/os' /etc/yum.repos.d/CentOS-Linux-FastTrack.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[ha\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/HighAvailability/$basearch/os' /etc/yum.repos.d/CentOS-Linux-HighAvailability.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[plus\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/centosplus/$basearch/os' /etc/yum.repos.d/CentOS-Linux-Plus.repo
sudo sed -i -e '/mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=/ s/^#*/#/' -e '/baseurl=http://mirror.centos.org/$contentdir/$releasever// s/^#*/#/' -e '/^\[powertools\]/a baseurl=https://mirror.rackspace.com/centos-vault/8.5.2111/PowerTools/$basearch/os' /etc/yum.repos.d/CentOS-Linux-PowerTools.repo

Alternatively, you can use the -f flag (e.g., sudo bash almalinux-deploy.sh -f) to handle this automatically.

Make a system backup. Not every possible scenario has been tested, so there's a chance something might go wrong. Having a backup ensures you have a restore point.

Download the almalinux-deploy.sh script:

$ curl -O https://raw.githubusercontent.com/AlmaLinux/almalinux-deploy/master/almalinux-deploy.sh

Run the script and check its output for any errors:

$ sudo bash almalinux-deploy.sh
  ...
  Migration to AlmaLinux is completed

A system reboot is recommended to boot into the AlmaLinux kernel:
```
sudo reboot
```

Verify that the conversion was successful:

# check release file
$ cat /etc/redhat-release
AlmaLinux release 8.5 (Arctic Sphynx)

# check that the system boots AlmaLinux kernel by default
$ sudo grubby --info DEFAULT | grep AlmaLinux
title="AlmaLinux (4.18.0-348.el8.x86_64) 8.5 (Arctic Sphynx)"

Thank you for opting for AlmaLinux!