[systemd-devel] ExecStart vs ExecStartPre

[Steven Noonan]

Hi there,

I'm wondering what the functional difference is between doing:

ExecStartPre=/bin/foo
ExecStart=/bin/bar

and

ExecStart=/bin/foo
ExecStart=/bin/bar

>From my read of the systemd.service man page, they appear to have the
same behavior in the common use case.

The only difference I can see is that groups of ExecStartPre and
ExecStart groups can be rearranged. That is, you could have an
ExecStartPre line *after* the ExecStart line in the file, and the
ExecStartPre would still be executed first. But the ordering of
multiple ExecStart (or ExecStartPre) lines in a single systemd.service
file matters, because it has explicit ordering as written in the file.

Why would someone choose one over the other? What differences am I missing?

- Steven