[Users] How to determine a container from the filesystem?

[Brad Alexander]

I just found out through the proxmox-ve forums that running ntp on a
container is considered a Bad Thing. So I am reworking my puppet
installation to disable ntp on the containers...But I was trying to
figure out a foolproof way of looking on the machine and determining
if it is a container or not. The only thing I have found so far is
that /proc/mtrr exists on the physical servers, but not on the
containers. Is this a viable way to make this determination or is
there a better way?

Thanks,
--b