Control groups (cgroups) in Linux are used to account and limit resources of groups of processes. For example, cgroups are used to account CPU usage and let us configure quotas and memory limits. cgroups are one of the foundation blocks of vpsAdminOS: every VPS has its own cgroup and can of course create its own nested cgroups. This is usually handled by the init system and so you don't work with cgroups directly.

There are two cgroup versions: v1 and v2. Because VPS are containers, the cgroup version depends on the host and cannot be changed inside VPS. Most VPS are currently using cgroup v1. This version is slowly being deprecated and we can expect its support to be removed from systemd in the near future (systemd v256 should still work).

The situation is complicated by the fact that older distributions do not support cgroups v2 and one node can use only one cgroup version. We have nodes with v1 for older VPS and nodes with v2 for new VPS and distributions that support it. You can see what cgroup version invididual nodes are using on vpsAdmin landing page. Our end goal is to move as many VPS as possible to cgroup v2, since it also comes with performance benefits e.g. in the memory subsystem.

The following distributions support cgroups v2:

• Alpine Linux with up-to-date init script
• CentOS / Alma Linux / Rocky Linux >= 8
• Debian >= 9
• Devuan with up-to-date init script
• Fedora >= 31 (possibly older)
• NixOS >= 19.03 (possibly older)
• openSUSE Leap >= 15.1 (possibly older)
• Ubuntu >= 18.04
• Void Linux with up-to-date init script

You can configure the cgroup version that the VPS requires. For most configurations, it should be enough to rely on cgroup v2 support in the distribution. The default setting is thus to allow whatever cgroup version the distribution works with. VPS with distributions that support v2 will be moved to nodes with v2 over time.

If your VPS requires a specific cgroup version and it's not possible to change it, you can reflect this in vpsAdmin settings. If you'd like to move to a node with a different cgroup version, please contact our support.