Automatic fsck

[Lars Wirzenius]

ke, 2008-08-13 kello 18:33 -0400, Phillip Susi kirjoitti:
> Andrew Sayers wrote:
> <snip>
> > I assume that the equivalent of "umount $snapshot" is done within the
> > kernel when the snapshot is created, because it gives you a new
> > non-mounted block device.  It's therefore possible to do fsck from cron.
> 
> The snapshot was never mounted in the first place, so there is no need 
> to unmount it.

Right. Just to be clear, the following would be a reasonably reasonable
scenario for boot-time fsck, in situations in which LVM snapshots are
available:

* kernel mounts root filesystem read-only
* init scripts make LVM copy-on-write snapshot of all filesystems
* init scripts re-mount root filesystem read-write, mount any other
filesystems
* fsck starts on each snapshot, preferably with "ionice -c3"
* once a snapshot has been checked, it is destroyed

Since the fscks can take a long time, the results can't be reported at
boot-time, and an alternative communication channel is needed. For
servers, e-mail and syslog seem reasonable.

Any problems found with the snapshots will _not_ be fixed in the real
filesystem, only in the snapshot. The real filesystem needs to be fixed
too. Like Matt suggested, marking the filesystem dirty (so a real fsck
is run at next boot) seems like a reasonable way of doing that.

For desktops, putting errors into /var/log/background-fsck/foo.log and
having something in the GNOME/KDE sessions watch those files and pop up
an error message should be feasible.

Would that work?