[systemd-devel] mount unit with special requirements

[Mantas Mikulėnas]

On Sat, Sep 8, 2018 at 8:20 PM Michael Hirmke <mh at mike.franken.de> wrote:

> Hi *,
>
> for my backups I use disks in a way similar to tapes.
> I have a fixed backup disk with one single partition, which is used for
> backing up the machine hosting this disk and a few other machines from
> remote. At night the contents from this disk get copied via rsync to a
> removable disk of the same size, which is replaced by another one next
> morning.
>
> For the backup "master" I have the following requirements:
>
> - 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.


>
> To achive that, at the moment my backup routine calls the following
> commands:
> - systemctl mask var-backup.mount
> - systemctl stop nfsserver smb (to avoid the partition being busy)
> - systemctl stop var-backup.mount
> - systemctl start nfsserver smb
> - fsck -yf /dev/sdf1
> - mount -o ro /dev/sdf1 /var/backup
> - (mount dup partition, fsck dup partition, rsync, umount dup partition)
> - mount -o remount,rw /dev/sdf1 /var/backup
> - systemctl unmask var-backup.mount
>
> It seems to be unnecessary complicated, but I didn't find a way to
> achive what I described above with a less complicated approach.
> Everything else I tried, led to problems with systemd, that tried
> to take unwanted actions. Even using the commands above, 1 out of 10
> jobs fails with messages like "Specified filename /dev/sdf1 has no
> mountpoint." when *stopping* var-backup.mount.
>

Can you be more specific about the messages you get? The closest I found to
yours was "Specified filename * is not a mountpoint" from the `fuser`
command – which is not called by systemd nor umount as far as I could grep.

(I would just use `umount /var/backup`, however.)

-- 
Mantas Mikulėnas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20180908/a8a93102/attachment.html>