RFE: provide /proc/sys/kernel/random/boot_id

[smoser]

As originally filed in ubuntu at bug 1831258 journalctl --list-boots identifies boots by reading /proc/sys/kernel/random/boot_id. Without doing this, the journal can only detect a reboot if the host has rebooted.

Without this ability to detect boots, functionality like journalctl --boot=X will also not work.

nspawn seems to do something similar in nspawn/nspawn.c:setup_boot_id

[brauner]

This is the wrong place. This should be done by the container at startup.

[xnox]

@brauner Where is the project for container startup? lxc? lxd? at first this looks no different to faking /proc/uptime. Cause each time /proc/uptime is faked, boot_id should be faked too. Or is this used for dynamic /proc files only, and static /proc files are faked somewhere else in container startup? I'm failing to find similar example as to where this should live then.

[brauner]

@brauner Where is the project for container startup? lxc? lxd? at first this looks no different to faking /proc/uptime. Cause each time /proc/uptime is faked, boot_id should be faked too. Or is this used for dynamic /proc files only, and static /proc files are faked somewhere else in container startup? I'm failing to find similar example as to where this should live then.

This should live in liblxc.

[brauner]

And be done at lxc_setup() time.

[stgraber]

Transferred over to liblxc, the runtime can indeed setup a memfd or something, put a uuid in there and bind-mount it (read-only) over the /proc file when it's in charge of mounting proc.