[systemd-devel] mount unit with special requirements

[Martin Wilck]

On Sat, 2018-09-08 at 19:55 +0200, Michael Hirmke wrote:
> Hi *,
> 
> [...]
> > > - The partition has to be mounted on boot.
> > > - It has to be unmounted before the nightly copy job, so that an
> > > fsck
> > >   can be performed.
> > > - After that it has to be mounted read only, so that during the
> > > copy
> > >   job no other machine can write to it.
> > > - After finishing the copy job, the partition has to be remounted
> > > read
> > >   write again.
> > > 
> > Isn't that commonly done using LVM? If it were on a logical volume,
> > you
> > could fsfreeze /var/backup (to suspend writes during snapshotting),
> > make a
> > LVM snapshot, thaw, mount the read-only snapshot elsewhere and
> > rsync off it.
> 
> I never used LVM and this system does not use an LVM partitioning.

fsfreeze should work without LVM. Of course you shouldn't be writing
tons of data to the file system while it's frozen, therefore LVM
snapshot + quick unfreeze would be more robust.

> 
> > (I would just use `umount /var/backup`, however.)
> 
> Can't do that as long as the mount unit is under systemd control.
> A few seconds later systemd remounts it on its own.
> 

"noauto" mount option?

Martin