Support for AlmaLinux

[Antony Messerli]

Add support for AlmaLinux to act as an alternative to CentOS. (https://almalinux.org/blog/almalinux-os-stable-release-is-live/) AlmaLinux OS is a 1:1 binary compatible fork of RHEL and has recently been marked as Stable. We should be able to add an alias for Redhat to Curtin so that it can be used in MAAS.

[Lee Trager (ltrager)]

In addtion to AlmaLinux there is also RockyLinux. I think Curtin should evaluate whether it can detect CentOS derivatives by looking at the ID_LIKE field in /etc/os-release instead of hard coding each derivative that is released.

[Igor Gnip (igorgnip)]

Getting curtin to do best effort match derivative to something it already supports is realistic and it would not prevent hardcoding any real differences on top of that if need be.

[Burkhard Linke (blinke)]

We are currently in the process to deploy a number of new nodes with MAAS and Almalinux 9. The missing support in curtin is a showstopper, but a fix is trival:

In https://git.launchpad.net/curtin/tree/curtin/distro.py

1. extend DISTRO_NAMES with 'almalinux'
2. add DISTRO.almalinux to redhat family

Using a patched MAAS snap and a matching custom image deployments of Almalinux boxes works fine for us. But we need this patch upstream for production.