> when using 'uptime' in containers (regardless what kind of containers), > it shows the uptime of the host system rather than the one of the container.
It _does_ work on vserver but not on lxc (and similar). 'uptime' is just a pretty-printer for /proc/uptime, you'd need to teach the kernel what a "container" means. And here's a problem: unlike vserver where containers are an in-kernel thing, lxc is merely a wrapper for chroot+cgroups+unshare. You can mix and match those yourself -- which raises the question when two processes stop being in the same "container". When their root filesystem differs? When they're in different namespaces -- but which namespace? I think the best approximation is the PID namespace -- ie, defining containers as "having separate inits". But when did the current init start? There _is_ task->real_start_time, ie, field 22 of /proc/1/stat, but it changes whenever init is exec()ed. What we'd want is the time when unshare was called, and I don't think that's stored anywhere. Thus, unless someone has a better idea, all we can get in modern containers is "time since init was started/upgraded". Meow! -- An imaginary friend squared is a real enemy.
