[pve-devel] [PATCH docs v2] pct: clarify needed systemd-versions for cgroupv2 support

[Stoiko Ivanov]

versions determined through systemd's changelog, and a few empiric
tests.

Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
---
changes v1->v2:
* fixed the wrong ubuntu-version in the note (I tested 16.04 LTS not 16.10)
Huge thanks to Thomas for catching this!!
 pct.adoc | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/pct.adoc b/pct.adoc
index b03b6ba..9c512df 100644
--- a/pct.adoc
+++ b/pct.adoc
@@ -518,8 +518,17 @@ Another important difference is that the 'devices' controller is configured in a
 completely different way. Because of this, file system quotas are currently not
 supported in a pure 'cgroupv2' environment.
 
-If file system quotas are not required and the containers are new enough to
-understand 'cgroupv2', it is recommended to stick to the new default.
+'cgroupv2' support by the container's OS is needed to run in a pure 'cgroupv2'
+environment. Containers running 'systemd' version 231 or newer support
+'cgroupv2' footnote:[this includes all newest major versions of container
+templates shipped by {pve}], as do containers not using 'systemd' as init
+system footnote:[for example Alpine Linux].
+
+NOTE: CentOS 7 and Ubuntu 16.04 are two prominent Linux distributions, which
+have a 'systemd' version that is too old to run in a 'cgroupv2' environment.
+
+If file system quotas are not required and the 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:
-- 
2.30.2