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pct: cgroup: update to cgroupv2 being the only supported mode

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As already mentioned in the known issues in the roadmap [0], cgroupv2
is the only supported mode in Proxmox VE 9.

To not break any references, because Proxmox VE 8 is not EOL yet, keep
the section about changing the cgroup version.

[0]: https://pve.proxmox.com/wiki/Upgrade_from_8_to_9#cgroup_V1_Removal

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
This commit is contained in:
Fiona Ebner
2025-08-14 15:59:23 +02:00
committed by Wolfgang Bumiller
parent 012c31e15a
commit c3f613396b
1 changed files with 7 additions and 20 deletions
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@@ -672,17 +672,11 @@ The main resources controlled via 'cgroups' are CPU time, memory and swap
limits, and access to device nodes. 'cgroups' are also used to "freeze" a
container before taking snapshots.
There are 2 versions of 'cgroups' currently available,
https://www.kernel.org/doc/html/v5.11/admin-guide/cgroup-v1/index.html[legacy]
and
https://www.kernel.org/doc/html/v5.11/admin-guide/cgroup-v2.html['cgroupv2'].
Since {pve} 7.0, the default is a pure 'cgroupv2' environment. Previously a
"hybrid" setup was used, where resource control was mainly done in 'cgroupv1'
with an additional 'cgroupv2' controller which could take over some subsystems
via the 'cgroup_no_v1' kernel command-line parameter. (See the
https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html[kernel
parameter documentation] for details.)
The current version of 'cgroups' is
https://www.kernel.org/doc/html/v6.14/admin-guide/cgroup-v2.html['cgroupv2'].
The https://www.kernel.org/doc/html/v6.14/admin-guide/cgroup-v1/index.html[v1 version]
of the cgroup subsystem was deprecated with the release of {pve} 7.0 and removed
entirely with {pve} 9.0. Before {pve} 7.0, a "hybrid" mode was the default.
[[pct_cgroup_compat]]
CGroup Version Compatibility
@@ -720,21 +714,14 @@ environment, you can either
* Move the container, or its services, to a Virtual Machine. Virtual Machines
have a much less interaction with the host, that's why one can install
decades old OS versions just fine there.
* Switch back to the legacy 'cgroup' controller. Note that while it can be a
valid solution, it's not a permanent one. Starting from {pve} 9.0, the legacy
controller will not be supported anymore.
====
[[pct_cgroup_change_version]]
Changing CGroup Version
^^^^^^^^^^^^^^^^^^^^^^^
TIP: If file system quotas are not required and all containers support 'cgroupv2',
it is recommended to stick to the new default.
To switch back to the previous version the following kernel command-line
parameter can be used:
Before {pve} 9.0, you could switch back to the previous version with the
following kernel command-line parameter:
----
systemd.unified_cgroup_hierarchy=0