systemd automount unit: run only when server is reachable

[Jürgen Bausa <Juergen.Bausa@xxxxxxxxx>]

Using Linux now for a long time I am still not really familiar with
systemd and have a question on its usage. Maybe this is the wrong place
to ask it. In this case please point me to an appropiate forum.

I am using systemd automount units (see below) to mount network shares
on my laptop (debian bullseye). This works fine in principle but I have
one big issue:

At home it is enough to set TimeoutSec to 2 s in the mount unit.
Normally the server is available and the share is mounted. If the server
is down I need to wait for just 2 s until I see it is not there. Thats ok.

But when not at home and using a vpn, the mount unit will not mount with
TimeoutSec set to 2 s. I need to set it to at least 10 s. Then the mount
works. But using 10 s means I always have to wait 10 s for each share
the system tries to reach and is not available. This is really annoying
when starting libreoffice for example (which seems to check for the last
used documents on startup).

What I would like to do is to put a test for server availabilty (e.g.
ping -c 1 $SERVER) into the automount file. When the server is not
available, automount is not run. Is this possible? Or do I need to
create a special unit and put something like

    Requires=nfs-server-online.target

in my automount unit? And how would the nfs-server-online unit look
like?

What I am doing at the moment is running a script that checks
availability of the nfs server every some seconds (via ping) and turns
on/off the automount unit accordingly (via systemctl start/stop
mnt-share.automount). This works, but its not a very elegant solution.
I am pretty sure it can be done better using systemd only.

Regards,

Jürgen

/etc/systemd/system/mnt-share.automount:
[Unit]
Description=autoount share

[Automount]
Where=/mnt/share
TimeoutIdleSec=1min

[Install]
WantedBy=multi-user.target




/etc/systemd/system/mnt-share.mount:
[Unit]
Description=Mount share

[Mount]
Where=/mnt/share
What=lana:/share
Type=nfs
Options=soft,async
TimeoutSec=10

[Install]
WantedBy=multi-user.target