[systemd-devel] How to keep certain services or mounts active during shutdown?

[Frank Steiner]

Hi,

Lennart Poettering wrote

>> 1. I want to keep the network running. To avoid problems with dependencies
>>    I had to keep it enabled although all the stuff is done in the kernel/initrd.
>>    Thus, it shuts down during reboot and the diskless client hangs
>>    of course.
> 
> This really depends on the network management service you are
> using. networkd won't shut down any network connections when you
> terminate it for example.
> 
> Which one are you using?

it's "wicked" in SLES 12 and it really shuts the network interface down
(might be configuration issue, though). I managed to keep it up by a 
drop-in conf with
ExecStop=
ExecStop=/usr/bin/true
(not sure if I need the second one, will check).

> Not sure if I grok why you want to do what you want to do (after all:
> if every user of your two NFS mounts are gone, why keep them around?),

Because we share / read-only with the server and mount only some
stuff (/var e.g.) for the client. To handle own runlevels we create
a tmpfs for /etc/systemd/system in dracut so the client can configure
its own runlevel dependencies.

The drop-in for avoiding the wicked shutdown is, of course, in this
tmpfs and could be unmounted before wicked tries to stop, thus, it
would fail to see the drop-in.

(This tmpfs was a NFS mount yesterday, that's why I wanted to keep it,
but we changed it to a tmpfs now).

> but you can do what you want by writing native .mount unit files for
> the file systems and the set DefaultDependencies=no. This will remove
> the implicit Conflicts= dependencies for shutdown.target. With those
> removed systemd won't try to unmount the mounts during the normal
> shutdown phase (unless there are mounts below them that are unmoutned, of
> course...).

That worked! I created a .mount file for the tmpfs with

DefaultDependencies=no
Before=network-online.target wicked.service

and so it was ordered after wicked during shutdown. 

> Note though that there are actual two shutdown phases: the normal one
> that strictly follows unit dependencies, and which you can influence
> this way. And a final one, that then tries to clean-up everything that
> was left over by that first phase. It's basically a umount loop that

That's ok as I only need to keep the mounts over a certain point, then
they can go :-)

Thanks for your help!
cu,
Frank




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