Lookie here: https://github.com/lxc/lxcfs/commit/9ac264cfb0836a013af6fa31a4e4c01afe72255a And, despite the commit message mentioning only /proc/stat, it also changes /proc/uptime so all is fine as long as the host has lxcfs >= 2.0.7-1.
This of course works only on containers started using lxc, rather than a zillion other chroot+cgroups+unshare wrappers, such as docker, systemd, etc. Meow! -- Don't be racist. White, amber or black, all beers should be judged based solely on their merits. Heck, even if occasionally a cider applies for a beer's job, why not? On the other hand, corpo lager is not a race.
