[systemd-devel] Reloading configuration after mount unit

[Norbert Lange]

Am Fr., 18. Juni 2021 um 16:35 Uhr schrieb Silvio Knizek <killermoehre at gmx.net>:
>
> Am Freitag, dem 18.06.2021 um 15:04 +0200 schrieb Norbert Lange:
> > Hello,
> >
> > I have an extra mount for /usr/local (Tools + Services which are just
> > useful for development), classically done vie /etc/fstab.
> >
> > Now there are a few systemd services within /usr/local/lib and systemd
> > does not seem to load/reload those and start the ones that add a
> > sysinit.wants.
> >
> > currently I have to do the following to get a "full start":
> > systemctl daemon-reload
> > systemctl start default.target
> >
> > What would be the correct way to cause systemd to reevaluate configuration?
> > I get that this generally could lead to bad behaviour (endless
> > reconfiguration if cycles),
> > but for something hierarchical like mount-paths it should be possible.
> >
> > I could think of a unit having an after/requires to usr-local.mount or
> > using a path unit watching PathChanged=/usr/local/lib/systemd.
> > At any rate, I am not sure how I could tell systemd to start new units
> > wanted by eg.
> > sysinit.target if this was already fully started. `systemctl start
> > default.target` seems
> > a bit dangerous.
> >
> > Another, less important issue is that I cant set lazy unmount in fstab.
> >
> > Norbert.
> Hi Norbert,
>
> make sure your /usr/local mount is done in the initrd and that you use
> »systemctl link /path/to/unit.service« to enable them.

That's not really helping, I don't want to chug in tons of tools in
the initramfs this is no desktop system.
systemctl link shouldnt be necessary, as /usr/local/lib/systemd/system
is a standard unit path.

Since there is a systemd-update-done that changes /etc I would have thought that
systemd rereads the configuration (as /etc/systemd/system could have
changed) during startup.
I would want that for /usr/local/lib/systemd/system after this path
was made available through a mount.

If systemd assumes the whole /usr drive to be static and has no way to
dynamically reload and "retarget"
(adding new wants/requires dependencies to starting/started targets)
then I guess that's the end of it.

I dont know if thats the case or if I just dont know how (as
systemd-update-done allows a changing /etc I would assume systemd
would rescan it for units/dependencies)

>
> For the automount behaviour, you need to add
> »noauto,x-systemd.autmount,x-systemd.idle-timeout=10s«
> to the options part in the /etc/fstab. See man:systemd.mount for more
> information.

Thats Automount, but I want "LazyUnmount",
and the suggestion kinda contradicts "make sure your /usr/local mount
is done in the initrd"

Norbert