Systemd with multiple execStart

if Type=simple in your unit file, you can only specify one ExecStart, but you can add as many ExecStartPre, ExecStartPost, but none of this is suited for long running commands, because they are executed serially and everything one start is killed before starting the next one.

If Type=oneshot you can specify multiple ExecStart, they run serially not in parallel.

If what you want is to run multiple units in parallel, there a few things you can do:

If they differ on 1 param

You can use template units, so you create a /etc/systemd/system/[email protected]. NOTE: (the @ is important).

[Unit]
Description=script description %I

[Service]
Type=simple
ExecStart=/script.py %i
Restart=on-failure

[Install]
WantedBy=multi-user.target

And then you exec:

$ systemctl start [email protected] [email protected]

or...

Target dependencies

You can create multiple units that links to a single target:

#/etc/systemd/system/bar.target
[Unit]
Description=bar target
Requires=multi-user.target
After=multi-user.target
AllowIsolate=yes

And then you just modify you .service units to be WantedBy=bar.target like:

#/etc/systemd/system/[email protected]
[Unit]
Description=script description %I

[Service]
Type=simple
ExecStart=/script.py %i
Restart=on-failure

[Install]
WantedBy=bar.target

Then you just enable the foo services you want in parallel, and start the bar target like this:

$ systemctl daemon-reload
$ systemctl enable [email protected]
$ systemctl enable [email protected]
$ systemctl start bar.target

NOTE: that this works with any type of units not only template units.

You can use ExecStartPre or ExecStartPost for one of scripts

[Unit]
Description=script description

[Service]
Type=simple
ExecStartPre=/script.py parameters1
ExecStart=/script.py parameters2
Restart=on-failure

[Install]
WantedBy=multi-user.target