Score:0

Ubuntu

Trying to get timing of systemd script right

Opux

3/26/24, 6:12 PM

I have this script that I'm trying to get the system to execute on shutdown and only on shutdown (or restart for that matter). This script doesn't start or stop a server; it merely unmounts some file systems. Unfortunately a lot of the documentation I find seems to think I'm going to write a script to manage a server, but that's not what I'm doing at all.

Reading http://tuxgraphics.org/npa/systemd-scripts/ and man systemd.service and man systemd.unit (I'm not even sure what I'm supposed to be following) I have:

[Unit]
Description=My umount script
After=network.target syslog.target

[Service]
Type=oneshot
ExecStop=/home/PL/bin/umountb2.sh
StandardOutput=journal

But I have no idea if that's right and I'm even less confident that it will be executed at the right time. I need it to execute sometime after all the regular users are logged out but not before any file systems are unmounted.

I'm running Ubuntu 22.04.2

Edit: now the config file looks like this:

 Description=My special shutdown script

 [Service]
 Type=oneshot
 RemainAfterExit=true
 ExecStop=/home/PL/bin/umountb2.sh

 [Install]
 WantedBy=multi-user.target

And things have improved, but there's a problem, because my script calls cryptsetup which returns an error. I think it's being executed too late, because when I restart, I run journalctl -b -1 --dmesg there are only 3 messages that follow my script, the first being:

kernel: nfsd: last server has exited, flushing export cache

0 + 10

shutdown

systemd

popey

3/26/24, 6:28 PM

Why do you need to even do this unmounting? The filesystem will get unmounted during the shutdown process anyway.

Opux

3/26/24, 6:40 PM

@popey Not if it mounts a file-based filesystem. It needs to first unmount that file system, then close the device in /dev, then it can proceed to unmount everything else

Doug Smythies

3/27/24, 12:05 AM

I think [this](https://unix.stackexchange.com/questions/39226/how-to-run-a-script-with-systemd-right-before-shutdown) might help.

Opux

4/1/24, 12:08 AM

@DougSmythies maybe it did a little. How can I know my script is being executed? I had some log messages expressed w/`echo` piped to `>&2` and some made w/`logger` but I don't see any of these messages in the logs

Doug Smythies

4/1/24, 12:44 AM

While I haven't tried it for awhile, I use `echo "doug_script $FWVER done..." >> /dev/kmsg` and then see it in `sudo dmesg`, but that gets scrubbed duing reboot (I think).

Doug Smythies

4/1/24, 12:51 AM

after you boot again, and doing the above type log entry, try `sudo journalctl -b -1 --dmesg | grep doug_script`, changing the search parameter to whatever you used. It worked for me.

Opux

4/1/24, 12:52 AM

@DougSmythies and that's after redirecting it to /dev/kmsg?

Doug Smythies

4/1/24, 12:56 AM

Yes. your redirect to /dev/kmsg is done during the script execution during shutdown, hopefully before kernel logging has been terminated. Then you should be able to see the message the next time you start the computer using the journalctl command.

Opux

4/1/24, 11:46 PM

@DougSmythies Yep. That did it. Thx

Opux

4/16/24, 6:24 PM

@DougSmythies Actually, there's still a problem and I think it's down to timing. I've edited my question which proposes the script be called earlier.

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EN: Trying to get timing of systemd script right

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