Add a systemd script (#50)

[davidcoutadeur]

Fixes #50

[davidcoutadeur]

This PR only takes care about adding the systemd files. Integration in debian / red-hat will be done elsewhere.

[davidcoutadeur]

On more point to check in this PR: describe the way to duplicate the sync/async systemd script to have more than one task.
Possible leads:

• overload systemd script (systemctl edit)
• use systemd instances

We need to clarify this in documentation, and also define if admins should use /etc/default for LSC_CONFIG_DIR, LSC_SYNC_TASKS,...

[davidcoutadeur]

On more point to check in this PR: describe the way to duplicate the sync/async systemd script to have more than one task. Possible leads:

* overload systemd script (systemctl edit)

* use systemd instances

We need to clarify this in documentation, and also define if admins should use /etc/default for LSC_CONFIG_DIR, LSC_SYNC_TASKS,...

We can only pass one parameter to a systemd instance.

But admins can still use systemd instances for defining the path to /etc/default/lsc to load.

[davidcoutadeur]

I have provided an example of systemd instance in 527a318

Not tested yet, but it should do the job. @xavierba if you have any remark? @coudot don't hesistate if you have an opinion on this topic.

[davidcoutadeur]

As pointed out by @xavierba , we should take advantage of this issue to drop the support of init.d.
I am favourable for doing so, because systemd is now the default component:

• since centos 7
• since debian 8

Anyway, we no longer support lsc packages for OS older that these.

If everyone is ok with that, I am going to remove init.d in #260

[davidcoutadeur]

systemd scripts seems ready in #260
I am going to merge.

What I have done since last review:

• removed /etc/init.d/lsc support
• removed useless sed on /etc/default/lsc-* files (since these variables are now defined in corresponding systemd unit files)
• fix pid filename directly in systemd unit file
• removed %systemd_preun [email protected] since systemd doesn't know which instance to stop (even with a joker)
• removed /etc/default/lsc (since not used any more)
• clean and simplify /etc/default/lsc-sync and /etc/default/lsc-async
• write the documentation (see https://github.com/lsc-project/documentation/blob/main/source/run.rst#using-systemd-service)
• test build + install + run + remove on debian12: OK
• test build + install +run + remove on rocky9: OK (warnings during preinstall, but not due to systemd)
• split long lines