Run a Script Before Shutdown or Reboot with systemd

This pattern starts your script whenever the machine is shutting down, whether the final action is reboot or poweroff. Use it when you want one system-wide cleanup script during every shutdown transition — not tied to a single application service.

shutdown.target is the systemd target used while the system is transitioning toward shutdown. systemd includes your service in that transaction through WantedBy=shutdown.target.

Do not assume another service such as a database or network connection is still available. If your script depends on one particular service, it is usually better to run that cleanup as part of that service's shutdown with ExecStop= — see create a systemd service.

When you need a script only on halt and not on reboot, use shutdown-only systemd unit instead.

Create the cleanup script

Append one line to a log file on each shutdown transition:

sudo tee /usr/local/sbin/before-shutdown-task.sh <<'EOF'
#!/bin/bash
LOG=/var/log/before-shutdown-task.log
echo "time=$(date -Is) shutdown_task_ran" >> "$LOG"
EOF

Make it executable:

sudo chmod 755 /usr/local/sbin/before-shutdown-task.sh

Create the shutdown service

Create /etc/systemd/system/before-shutdown-task.service:

[Unit]
Description=Run task before shutdown or reboot completes
DefaultDependencies=no
Before=shutdown.target

[Service]
Type=oneshot
ExecStart=/usr/local/sbin/before-shutdown-task.sh

[Install]
WantedBy=shutdown.target

Enabling this unit makes systemd include it during the normal shutdown transaction on both reboot and poweroff.

WantedBy= decides which systemd transaction pulls the service in. Before= decides its ordering inside that transaction. Here, shutdown.target pulls it in for both reboot and poweroff, and Before=shutdown.target makes the script finish before that synchronization point.

This does not mean every other service is still running when your script starts.

Reload and enable

Reload unit definitions after editing the file:

sudo systemctl daemon-reload

Enable the unit for shutdown and reboot transitions:

sudo systemctl enable before-shutdown-task.service

Sample output:

Created symlink '/etc/systemd/system/shutdown.target.wants/before-shutdown-task.service' → '/etc/systemd/system/before-shutdown-task.service'.

Verify after reboot or poweroff

Reboot or run sudo poweroff on a test VM. After the system is back, read the log the script writes:

sudo cat /var/log/before-shutdown-task.log

Sample output from lab testing:

time=2026-08-21T11:05:41+05:30 shutdown_task_ran
time=2026-08-21T11:13:41+05:30 shutdown_task_ran

Each line shows the unit ran during a shutdown transition. To run only on poweroff and skip reboot, use the shutdown-only guide.

If persistent journal storage is enabled on your system, you can also inspect the previous boot:

journalctl -u before-shutdown-task.service -b -1 --no-pager

Troubleshooting

References

• systemd.special(7) — shutdown.target
• systemd.service(5)

Summary

A shutdown hook uses WantedBy=shutdown.target so systemd pulls your script into reboot and poweroff shutdown transactions, and Before=shutdown.target so the script finishes before that synchronization point. Verify with the log file under /var/log/; use journalctl -b -1 only when persistent journal storage is available.

To run only on poweroff and skip reboot, use the shutdown-only pattern in the linked guide.