How to start service in systemd right after cryptsetup

systemd

I have an ArchLinux installation with systemd. I am trying to run a hook immediately after my encrypted data device is mounted in order to put flashcache on top of it. I have scripts that work, however I cannot make them load in right order. Here's what I did:

file: /usr/lib/systemd/system/flashcache.service

[Unit]
Description=FlashCache
Requires=systemd-cryptsetup@cdata.service

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/local/bin/flashcache_startup_script

[Install]
WantedBy=dev-mapper-data_cached.device

After creating file, I ran systemctl enable flashcache.service.

However, on boot it does not start, the dev-mapper-data_cached times out, after which I can get into a root shell and run flashcache_startup_script manually.

I examined output of journalctl -b, and determined that FlashCache service does not load before timeout occurs.

Another option I tried without success is Requires=dev-mapper-vg1-data.device

What am I doing wrong?

Best Answer

I tried all sorts of things, mainly using following resource. I am not exactly sure why it worked, but following unit file solved the issue:

[Unit]
Description=FlashCache
BindsTo=dev-vg1-data.device
After=dev-vg1-data.device
DefaultDependencies=no

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/local/bin/flashcache_startup_script

[Install]
WantedBy=sysinit.target

Related Solutions

Make systemd reload only single openvpn process and not the whole group

If you use CONFIGNAME as your config file name for your .conf file you could try

systemctl restart openvpn@CONFIGNAME.service

Systemd linked unit files on mounted disk fail to load

As explained by @StephenHarris the problem is at the moment systemd tries to read the unit, the file that's symlinked isn't available yet

To just have systemd reload the units after it has mounted :

[Unit]
Description=reloads units stored in /mnt/data
DefaultDependencies=no
After=mnt-data.mount
Requires=mnt-data.mount

[Service]
Type=oneshot
ExecStart=/bin/systemctl daemon-reload

[Install]
WantedBy=local-fs.target

This will cause the units to become available, because this time this time the target of the symlinks is mounted.

But by that time, the list of jobs needing to be run to reach the default.target is already built, and the service won't be started.

To have it also restart your service:

[Unit]
Description=restart unit stored in /mnt/data
Requires=mnt-data.mount

[Service]
Type=oneshot
ExecStart=/bin/systemctl daemon-reload
ExecStartPost=/bin/systemctl start sprinterd.service

[Install]
WantedBy=multi-user.target

Alternatives:

I've tested with ExecStart= & ExecStartPost=, but it should obviously work with ExecStartPre= & ExecStart=
if it's all about 1 single unit, you might as well : ExecStart=/bin/systemctl enable /mnt/data/sprinterd.service instead of daemon-reload
if there are multiple services, do the daemon-reload, then start a single unit that uses ConsistsOf= or PartOf= to load all the multiple services.
If its NFS (or other networked system), of course local-fs.target isn't your best Installation option, obviously.

For a more old-school SysVinit-style approach, put the systemctl commands inside /etc/rc.local and chmod +x that file.

And then go smuggly post on Devuan's mailing list how you needed SysVInit to fix b0rked SystemD ;-)

Best Answer

Related Solutions

Make systemd reload only single openvpn process and not the whole group

Systemd linked unit files on mounted disk fail to load

Related Question