Hey guys, I have question regarding a certain behaviour of the systemd
mount generator.
Mounts do not have `Before=*-fs.target` if the `nofail` mount option is
added to their `/etc/fstab` entry.
From the man page I see that this is intended behaviour:
-
https://www.freedesktop.org/software/systemd/man/latest/systemd.mount.html#Default%20Dependencies
-
https://www.freedesktop.org/software/systemd/man/latest/systemd.mount.html#noauto
First of all, I see the reason why it seems to be not important for
mounts to start before certain targets, if one explicitly declares that
it is okay for them to fail. But I do not see a downside of adding
`Before=*-fs.target` either. There are use cases where one still wants
other services to wait for at least the attempt to have all network
shares mounted, even when not wanting some of them to cause failure in
the boot sequence.
The more problematic implication however is indeed, that those mounts
can be attempted to be unmounted on shutdown, before services with
`After=*-fs.target` are stopped. This can lead to hanging services and
potential data loss. It has been observed with qBittorrent and a CIFS
network share in particular, where the CIFS mount was tried to be
unmounted first, failed, since it was accessed by qBittorrent, and for
some reason was hanging the shutdown sequence, so that the system needed
to be power cycled. Doing the unmount manually before shutdown, solves
the issue. This was when I found the missing `Before=remote-fs.target`
entry.
Is there a particular reason `nofail` mounts do not have
`Before=*-fs.target` defined, respectively is there any downside when
defining it as well with `nofail`? One thing I have in mind, is that
hanging mount attempts delay `remote-fs.target` and hence
`getty@.service` units, i.e. the local login prompt. However, if I want
to avoid this, because I am expecting the share to be offline regularly,
then I would would use `noauto`, in case with `x-systemd.automount`. But
I did not expect the `nofail` option to be a "mount at any later time on
boot" + "unmount at any earlier time on shutdown".
Best regards,
Micha
