On Wed, Feb 17, 2016 at 2:01 PM, Andrew Savchenko <birc...@gentoo.org> wrote:
> 1) NFS v4 shares can't be unmounted if server is unreachable (even
> with -f). If filesystem (e.g. /home or /) contains such unmounted
> mount points, it can't be unmounted as well, because it is still in
> use. This happens quite often if both NFS server and client are
> running from UPS on low power event (when AC power failed and
> battery is almost empty).

Perhaps at least the behavior in this case should be configurable
(timeouts, infinite or otherwise).

If you can't contact a remote nfs server then I believe it is possible
that unwritten changes are in buffers/etc.  Depending on circumstances
I could see either pausing until the server comes back or discarding
changes and powering off could either be the appropriate behavior.

Ultimately, anything not on the disk is always at risk, and any
filesystem needs to provide for unclean shutdown to be truly robust.
A kernel panic/etc could cause loss of all data in buffers without
warning.  However, barring that we should of course engineer openrc to
shut down in the most clean manner possible, and this should include
read-only mounts for anything which can't be unmounted.

And even systemd+dracut struggles to cleanly unmount NFS roots in the
versions I'm running at least, so that is an edge case that doesn't
get much testing.


Reply via email to