[systemd-devel] elegant way to use a single mount unit file for multiple paths

[François]

Hi,

I’m not sure, but can’t systemd-tmpfiles get this sorted for you ?

See https://www.freedesktop.org/software/systemd/man/systemd-tmpfiles-setup.service.html

Good luck :-)

-- 
François


> Le 22 janv. 2020 à 18:59, Marcel Partap <mpartap at gmx.net> a écrit :
> 
> Salut,
> for our live debian USB stick distro for students ( https://github.com/fsfw-dresden/usb-live-linux ), we want to minimize on flash writes by putting several paths into a tmpfs overlay. So there is a pre-overlay at .service with
> 
>> [Unit]
>> Description=Prepare writable overlay on %f
>> DefaultDependencies=no
>> RequiresMountsFor=/run
>> 
>> [Service]
>> Type=oneshot
>> ExecStart=/bin/mkdir -p '/run%f'
>> ExecStart=/bin/mount -t tmpfs -o noatime tmpfs '/run%f'
>> ExecStart=/bin/mkdir -p '/run%f/work' '/run%f/rw'
> 
> and f.e. a var-lib-apt-lists.mount with
>> [Unit]
>> Description=tmpfs overlay of %f
>> Conflicts=umount.target
>> Wants=pre-overlay@%p.service
>> After=pre-overlay@%p.service
>> 
>> [Mount]
>> What=overlay
>> Type=overlay
>> Where=%f
>> Options=lowerdir=%f,upperdir=/run%f/rw,workdir=/run%f/work
>> 
>> [Install]
>> WantedBy=local-fs.target
> 
> Currently, the file is just cloned for multiple paths, which is working but not very elegant. I tried changing it into an instanced unit file tmpfs-overlay at .mount, which did not work ("Unit type mount cannot be templated" in journal only, nothing from systemd-analyze verify or the systemd.mount man page).. Neither did calling the file tmpfs-overlay.mount.unit and symlinking to it as var-lib-apt-lists.mount, var-cache-apt.mount etc.
> 
> So what would be a more elegant way to not have multiple copies of the very same file?
> 
> Best Regards,
> #marcel
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