Virtualizing /proc/sys/kernel/random/boot_id per container ?

["Daniel P. Berrange" <berrange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

One of the features that SystemD folks have asked us to fix in LXC, is
to make sure that /proc/sys/kernel/random/boot_id changes each time a
container is started.

The current semantics are that this file produces a new random UUID each
time the host OS is booted. Obviously each time we start a container now,
they just see the host's random boot_id, so from a container's POV this
does not change each time it starts.

There seems to be general agreement that, aside from the PID directories,
changes to data in  proc should be done by a FUSE filesystem overlay of
some kind. We could use that mechanism to fix 'boot_id' in userspace, but
I'm wondering if this is a better candidate for dealing with in kernel
space, since as well as the /proc/sys tree, the data is also visible via
the sysctl() system call which a FUSE overlay won't address.

The kernel doesn't have a real concept of a 'container' to associate
a boot_id value with as such, but maybe it is reasonable to associate
a boot_id value with each PID namespace ?

Regards,
Daniel
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