Container fails with cgroup error

When running a systemd container on an OpenRC host, you may encounter cgroup-related errors preventing the container from starting properly.

The fix is to explicitly mount cgroups in the container configuration:

lxc config set [container] raw.lxc 'lxc.mount.auto = cgroup'

This tells LXC to automatically mount the cgroup filesystem inside the container, which systemd requires for service management.