Several rituals have established themselves with great regularity in the past IT decade. Only recently, version 24 of the free cloud environment OpenStack, which Canonical patron Mark Shuttleworth once made the standard cloud in Ubuntu and thus gave the project a powerful boost, was released on schedule. And because OpenStack and Ubuntu are still very closely linked, experienced system administrators know: Where a new OpenStack version appears, a new Ubuntu release cannot be far away. Canonical released Ubuntu 21.10 recently, as planned, in mid-October.
Even if you prefer the LTS version, you should already look into the new features of the server: Most of them will also be found in Ubuntu 22.04, the upcoming LTS version.
CGroups v2 are now the standard
The “control groups”, or “CGroups” for short, are a kernel feature in Linux with the help of which the use of resources for a group of processes can be restricted by a central instruction. They go hand in hand with the namespaces that isolate different process groups on Linux systems from one another. Both functions are essential for the operation of containers. There are still two versions of the CGroups in the Linux kernel – and in Ubuntu 21.10 the changing of the guard longed for by many admins takes place: The CGroups v2 are from now on the standard procedure. Programs that only CGroups in version 1 understand, then fly on the nose: While the first implementation was still attached to threads at the system level, version 2 uses processes as a distinguishing feature.
This affects, for example, how the kernel displays the implemented CGroups in SysFS. If a program calls up this information and finds the v2 hierarchy, although it can only interpret the v1 hierarchy, crumbs are created. If you rely on popular software such as Docker or Podman, you have no reason to worry: You mostly implemented CGroups v2 months ago. If you use programs you have written yourself, you should prepare them for operation with CGroups v2 as soon as possible or adjust the compatibility settings of the kernel.
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By the way: Ubuntu 21.10 comes quite late to the CGroups v2 party. The Debian GNU / Linux on which the distribution is based has relied on CGroups v2 ex works since the recently released version 11 – like most other distributions. At Canonical, the limited v2 support for the Snap package manager, which is not particularly popular in the community, was the reason for the change that has only just taken place.
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