Executing a command before starting a systemd service

Question

I want to execute a script before starting a service every time the service is started.

I know that I can use ExecStartPre inside the service definition file, but I wonder if it's possible to achieve without editing a file which comes from the service's package.

The script is a simple command which exits when it's done, it creates files which are used by the main service (it fetches TLS certificates and keys from secure storage).

Does this answer your question? Modify systemd unit file without altering upstream unit file — Bob, Feb 03 '21 at 13:47
@HermanB yes it looks like the second option in the accepted answer does what I need. The service change is done in batch (as part of AMI creation with Packer), so the "manual" steps make more sense in my context instead of using the interactive systemctl edit. But it's good to learn. — Capt. Crunch, Feb 03 '21 at 22:00

score 6 · Accepted Answer · edited Feb 04 '21 at 13:57

6

Sure. You can use specific independant includes:

mkdir /etc/systemd/service/<servicename>.service.d
echo /etc/systemd/service/<servicename>.service.d/<anything>.conf << EOF
[Service]
ExecStartPre=<path to script>
EOF
systemctl daemon-reload

et voila.

Reference: Search for "drop-in" in systemd.unit — Unit configuration

edited Feb 04 '21 at 13:57

Capt. Crunch

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answered Feb 03 '21 at 06:43

drookie

8,759

Thanks. This worked. I made some corrections and improvements to the answer. – Capt. Crunch Feb 03 '21 at 21:53

Executing a command before starting a systemd service

1 Answers1