[pve-devel] applied: [PATCH v2 docs] pct: cgroup: update to cgroupv2 being the only supported mode

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

applied, thanks

On Thu, Aug 14, 2025 at 03:59:23PM +0200, Fiona Ebner wrote:
> 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>
> ---
> 
> Changes in v2 (thanks, Thomas!):
> * Improve initial section mentioning the two versions.
> * Keep section about changing cgroup version to not break any
>   references.
> 
>  pct.adoc | 27 +++++++--------------------
>  1 file changed, 7 insertions(+), 20 deletions(-)
> 
> diff --git a/pct.adoc b/pct.adoc
> index 529b72f..d6146eb 100644
> --- a/pct.adoc
> +++ b/pct.adoc
> @@ -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
> -- 
> 2.47.2


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