systemd and mounting filesystems

[Steven Whitehouse]

Hi,

I'm looking for some info on systemd and how filesystems are mounted in
Fedora. I've started looking into converting the gfs2-utils package to
the new init system and run into things which are not documented (so far
as I can tell).

Currently there are two init scripts in gfs2-utils, one is called gfs2
and the other gfs2-cluster.

Converting gfs2-cluster is trivial. It simply runs the gfs_controld
daemon on boot.

The more complicated conversion is the gfs2 script. This has been used
historically to mount gfs2 filesystems (rather than using the system
scripts for this). I assume that under the new systemd regime it should
be possible to simply tell systemd that gfs2 filesystem mounting
requires gfs_controld to be running in addition to the normal filesystem
requirement of having the mount point accessible, and then systemd would
do the mounting itself.

Things are slightly more complicated in that gfs_controld is only a
requirement for gfs2 when lock_dlm is in use. For lock_nolock
filesystems, mounting is just like any other local filesystem. The
locking type can be specified either in fstab, or in the superblock
(with fstab taking priority).

Another issue which I suspect is already resolved, but I'm not quite
sure how it can be specified in fstab, etc, is that of mount order of
filesystems. In particular how to set up bind mounts such that they
occur either before or after a specified filesystem?

I hope to thus resolve the long standing bug that we have open (bz
#435096) for which the original response was "Wait for upstart" but for
which I'm hoping that systemd can resolve the problem.

So I'm wondering how to express these requirements in systemd correctly,

Steve.