Tag Archives: systemd

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Run a Linux systemd service during shutdown

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I recently needed to add a cleanup service that runs at shutdown to a hundred AWS servers. My requirements were:

  • Run the script /usr/local/sbin/ec2-cleanup.sh when a VM shuts down (poweroff or reboot).
  • Send the output from the script to the syslog service.

So I needed to create a systemd service file that would call the script when the VM shuts down. This is the ec2-cleanup.service file I created:

# ec2-cleanup.service

[Unit]
Description=Run cleanup at shutdown
After=syslog.service network.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStop=/usr/local/sbin/ec2-cleanup.sh
Restart=on-failure
RestartSec=1s

[Install]
WantedBy=multi-user.target

Type=oneshot means that the command runs once. Normally since this is a oneshot service the service would exit after the ExecStart command runs, but since I don’t want to do anything when the service starts, there is is no ExecStart command. That’s why I use RemainAfterExit=yes, which keeps the service running even though there’s no ExecStart command.

Finally I use ExecStop to run the command at shutdown time.

After=syslog.service network.target ensures that the ec2-cleanup.service doesn’t start until after syslog service is running and the network has started. More importantly, since systemd stops services in the reverse order that they’re started, this also ensures that syslog and the network service are still running when systemd runs the ec2-cleanup.service‘s ExecStop command.

Although there are many different available syslog services, most use “syslog” as a service alias, so After=syslog.service should work regardless of which syslog service you actually use. (e.g. If you use rsyslog this still works, because rsyslog declares syslog as an alias.)

Finally, I just needed to install the service on my AWS VMs, so I added this to an Ansible playbook that runs on my AWS VMs:

  - name: Install the ec2-cleanup.sh script
    copy:
      src: ec2-cleanup.sh
      dest: /usr/local/sbin/ec2-cleanup.sh
      owner: root
      group: root
      mode: 0755

  - name: Install a service to run ec2-cleanup.sh at shutdown
    copy:
      src: ec2-cleanup.service
      dest: /lib/systemd/system/ec2-cleanup.service
      owner: root
      group: root
      mode: 0644
    register: ec2_cleanup_service

  - name: Restart ec2-cleanup service if the service file changed
    systemd:
      name: ec2-cleanup
      daemon_reload: True
      state: restarted
    when: ec2_cleanup_service.changed

  - name: Enable ec2-cleanup service so it starts on boot
    systemd:
      name: ec2-cleanup
      enabled: True
      state: started

To verify that all of this works I ran the Ansible playbook on a VM, then logged in and checked the status of the service:

eruby@i-056ac231adeb1f930:~$ systemctl status ec2-cleanup
● ec2-cleanup.service - Run cleanup at shutdown
     Loaded: loaded (/lib/systemd/system/ec2-cleanup.service; enabled; vendor preset: enabled)
     Active: active (exited) since Tue 2023-03-14 17:04:37 UTC; 44s ago

Mar 14 17:04:37 i-056ac221aceb1f830 systemd[1]: Finished Run cleanup at shutdown.

The service is active (exited), which I expected (exited because ExecStart has completed, active because RemainAfterExit=yes is keeping the service running until shutdown.

If I reboot the VM and log back in I can check syslog with:

journalctl -u ec2-cleanup.service -n 20

… and see the last 20 lines of output from the script. The log output shows that the script ran when I rebooted.

Hope you find this useful.

Getting rid of the “redirecting to systemctl” message in OpenSUSE

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On OpenSUSE systems running systemd all rcX scripts now redirect start, stop, reload, restart, etc. service commands to systemctl. The messages that  used to appear on STDOUT telling you that a command is successful (or not) are now logged, but are no longer displayed on STDOUT.

That I can deal with, but every call to an rcX script now generates the message “redirecting to systemctl” to STDERR. I have a lot of scripts that call rcX scripts, and they interpret STDERR messages as “something just broke”.

The culprit is the new /etc/rc.status script that ships with OpenSUSE. It spews out the “redirecting to systemctl” message to STDERR for every operation that you do. The following command will modify the script and remove this stupid message:

if ( grep -q 'redirecting to systemctl' /etc/rc.status ) ; then
    # Save a copy of the original file
    cp -p /etc/rc.status /etc/rc.status.orig;

    # OpenSUSE 12.1:
    perl -i.bak -pe 's,echo "redirecting to systemctl" >/dev/stderr,,;' /etc/rc.status;

    # OpenSUSE 12.3:
    perl -i.bak -pe 's,echo "redirecting to systemctl \${SYSTEMCTL_OPTIONS} \$1 \${_rc_base}" 1>&2,,;' /etc/rc.status;
fi

This works for OpenSUSE 12.1 and 12.3. I did not have a 12.2 system available to test with.

Hope you find this useful.