[lxc-devel] [RFC] rootfs pinning

[Christian Seiler]

Hi there,

just a quick question: currently, rootfs is pinned with a .hold file in
the parent directory (which btw. does not help against file systems that
are already mounted on the host but directly in the rootfs directory).
The problem with the .hold file is that it doesn't make the directory
necessarily pretty; I tend to mount all rootfs to /srv/lxc/$container
(config remaining in /var/lib/lxc), and then when doing a ls /srv/lxc, I
see tons of .hold files. (I'm not even sure that they are removed after
container termination - but even if they are, the default state of a
typical system tends to be that at least some containers are running...)

Couldn't we just open $rootfs/lxc.hold for writing, keep the fd (as
current pinfd) and then unlink (!) the file directly? According to POSIX
semantics, the file is then still open and the pinning should work (now
also for the above case), but there are no files lying around anymore.
(Note: I didn't test that, it could well be that that doesn't work.)

Thoughts?

-- Christian