[systemd-devel] How to permanently disable a service after first boot

[Lennart Poettering]

On Fri, 27.09.13 12:26, Muhammad Shakeel (muhammad_shakeel at mentor.com) wrote:

> Hi,
> 
> If there is a foo.service which is required to run during first
> system boot then what is the best solution to permanently disable it
> afterwards?
> 
> I can think of two solutions but I am not sure which one is
> correct/more appropriate.
> 
> 1) ExecStartPost=systemctl disable foo.service (I doubt this will
> work)

This should work.

> 2) ExecStartPost=/bin/rm -f foo.service (this works for me but is
> this a clean solution?)

This is a bad idea. For most packaged software unit files are usually
shipped as part of an RPM, and stored in /usr. During normal boots /usr
is likely to be read-only. Hence you cannot remove those unit
files. Also, you should not remove unit files without disabling them,
hence you'd need #1 before this anyway.

> Is there any flag in for systemd unit files which can be set to run
> a service on first boot only?

My recommendation would be to use something like ConditionFileExists= on
some configuration or flag file and let the service enabled
unconditionally and always, but skipped in later boots. This is usually
the best thing to keep things as state-less as possible. This of course
applies only if what you are trying to do is for showing a configuration
dialog on first boot or so. This has the benefit that you actually bind
execution of your service to the actual existance of first time
configuration (which is probably what you really want to express, no?)
instead of the first boot (which only indirectly is what you want to
express, right?).

Hope that makes some sense...

More information on ConditionFileExists= and the other conditions you
find in "man 5 systemd.unit".

Lennart

-- 
Lennart Poettering - Red Hat, Inc.