Deprecated /var/run being used for tmpfiles.d

[bobvanderlinden]

Issue description

Currently there are a number of services that define something inside /var/run inside /etc/tmpfiles.d/*.conf. One example I ran into was kubernetes. Upon running nixos-rebuild it would show the following warning:

setting up tmpfiles
[/etc/tmpfiles.d/nixos.conf:6] Line references path below legacy directory /var/run/, updating /var/run/kubernetes → /run/kubernetes; please update the tmpfiles.d/ drop-in file accordingly.

/etc/tmpfiles/nixos.conf contained the following lines:

# This file is created automatically and should not be modified.
# Please change the option ‘systemd.tmpfiles.rules’ instead.

D! /tmp 1777 root root
d /opt/cni/bin 0755 root root -
d /var/run/kubernetes 0755 kubernetes kubernetes -
d /var/lib/kubernetes 0755 kubernetes kubernetes -
d /var/cache 0755 root root -

Apparently /var/run/kubernetes is deprecated and should be /run/kubernetes. I'll make a PR for this particular instance, but there are probably more instances of this happening.

Alternatively, #40594 might help in this regard as well as upstream projects will run into the same issue and will resolve this for themselves. We currently cannot always ride along with them.

Steps to reproduce

/etc/nixos/configuration.nix:

...
  services.kubernetes.roles = ["master" "node"];
...

Run nixos-rebuild switch and notice the warning.

[florianjacob]

Related WIP PR for resolving this tree-wide: #47856