systemd oneshot server to run every x days

Question

I was hoping to run a command every 85 days using systemd. I have created a timer and a service for the command, but I can't get the timer started. I am hoping to get the command to run every 85, not at boot and to run even if the server is restarted during the 85 day period.

/etc/systemd/system/my.service

[Unit]
description=Do my task

[Service]
Type=oneshot
ExecStart=/usr/local/sbin/myTask

/etc/systemd/system/my.timer

[Unit]
Description=Timer to do my task

[Timer]
OnUnitActiveSec=85d
Unit=my.service
Persistent=true

After attempts to start it using systemctl start my.timer, the error messages I have been getting are:

my.timer: Refusing to start, unit to trigger not loaded.
Failed to start Timer to do my task.

Answer 1

Change description in your service file to Description. Otherwise, it'll be printing errors in the logs like below:

Unknown lvalue 'description' in section 'Unit'

Also, try using these commands to troubleshoot problems with your timer file:

systemctl status my.timer
journalctl -xe

Update your post if you see any errors in the logs and don't know how to fix them.

Answer 2

The issue was the script I was trying to run didn't have a bang at the start.

I diagnosed it by:

1. looking at the status of the time Andril mentioned above

# systemctl status my.timer
● my.timer - Timer to update stuff
   Loaded: loaded (/etc/systemd/system/my.timer; enabled; vendor preset: enabled)
   Active: active (elapsed) since Tue 2020-01-28 07:14:54 UTC; 2 weeks 6 days ago
  Trigger: n/a

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

2. Looking at the list of timers (to get more stats about it)

# systemctl list-timers
NEXT                         LEFT        LAST                         PASSED                UNIT                         ACTIVATES
...
n/a                          n/a         Tue 2018-03-20 14:13:46 UTC  1 years 10 months ago my.timer            my.service

3. Tried running the service to activate the service (as the timer is based on the last time the service was activated

# systemctl status my.service
● my.service - Renew Lets Encrypt certificates
   Loaded: loaded (/etc/systemd/system/my.service; static; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2020-02-17 15:53:18 UTC; 20s ago
  Process: 19875 ExecStart=/usr/local/sbin/script (code=exited, status=203/EXEC)
 Main PID: 19875 (code=exited, status=203/EXEC)

Feb 17 15:53:18 server systemd[1]: Starting Update stuff...
Feb 17 15:53:18 server systemd[19875]: my.service: Failed to execute command: Exec format error
Feb 17 15:53:18 server systemd[19875]: my.service: Failed at step EXEC spawning /usr/local/sbin/script: Exec format error
Feb 17 15:53:18 server systemd[1]: my.service: Main process exited, code=exited, status=203/EXEC
Feb 17 15:53:18 server systemd[1]: my.service: Failed with result 'exit-code'.
Feb 17 15:53:18 server systemd[1]: Failed to start Update stuff.

4. By trial and error looked at the script and saw it didn't have a bang, so added one

# vim /usr/local/sbin/script
#!/bin/bash
echo Update!

5. Tried running the service again

# systemctl start my.service
# systemctl status letsencrypt.service
● my.service - Update stuff
   Loaded: loaded (/etc/systemd/system/my.service; static; vendor preset: enabled)
   Active: inactive (dead) since Mon 2020-02-17 16:05:45 UTC; 4s ago
  Process: 31781 ExecStart=/usr/local/sbin/script (code=exited, status=0/SUCCESS)
 Main PID: 31781 (code=exited, status=0/SUCCESS)

Feb 17 16:05:45 server systemd[1]: Starting Update stuff...
Feb 17 16:05:45 server test[31781]: Update!
Feb 17 16:05:45 server systemd[1]: Started Update stuff.

(woohoo)

6. Checked the timers again

# systemctl list-timers
NEXT                         LEFT                  LAST                         PASSED                UNIT                         ACTIVATES
...
Tue 2020-05-12 16:05:45 UTC  2 months 24 days left Tue 2018-03-20 14:13:46 UTC  1 years 10 months ago my.timer            my.service

x timers listed.
Pass --all to see loaded but inactive timers, too.

(now the timer shows that it is going to run again)