debian: remove invoke-rc.d calls from postrm scripts

[tchaikov]

Previously, we called invoke-rc.d ceph stop in postrm scripts to support sysvinit-based installations. However, this fails on systemd- based systems, which are now the default on modern Debian distributions.

When invoke-rc.d detects systemd as the init system, it delegates to systemctl, converting invoke-rc.d ceph stop to "systemctl stop ceph.service". Since Ceph provides ceph.target and template units (ceph-osd@.service, ceph-mon@.service, etc.) rather than a monolithic ceph.service, this command always fails with exit code 5 (LSB EXIT_NOTINSTALLED).

This failure prevents the auto-generated cleanup sections added by debhelper from executing properly, which can leave the system in an inconsistent state during package removal.

Changes:

• Remove the invoke-rc.d call entirely. Systemd will handle service cleanup through its own mechanisms when the package is removed.
• Remove redundant exit 0 statement (the script exits successfully by default, and set -e is no longer needed without commands that might fail).
• Remove vim modeline comment, as it's unnecessary for a 3-line script.

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[tchaikov]

cc @ThomasLamprecht

[ThomasLamprecht]

If one would be really "nice" one could check for the system running systemd or something else, but IMO it does not really make sense to run ceph on Debian without systemd.
Besides that, any downstream distribution can just re-add these (or similar ones) fitting their init stack more closely.

But all files that basically just have the #DEBHELPER# template stanza left [0] could be also deleted, as that's the default anyway.

[0]: i.e. look like:

#!/bin/sh

set -e

#DEBHELPER#

[jatinkumarsingh]

hey can i help u out mate

[tchaikov]

changelog:

• remove the 3-line stanaza as this is what debhelper provides us by default.

[tchaikov]

@ThomasLamprecht hi Thomas, thanks for the insights and suggestion. incorporated your suggestion.

tested at https://shaman.ceph.com/builds/ceph/wip-pr-66352-kefu/0b044bfb0a691f7cd19f34ee1ccf85daf6c2fc01/

i checked by uncompressing the .deb package, and verified that, after removing the .prerm file, the generated prerm is identical to the version generated with the 3-line stanza.

[tchaikov]

@alimaredia could you help review this change?

[ThomasLamprecht]

FWIW, this now looks OK to me as is.

[alimaredia]

@tchaikov I removed my review on this PR. I don't feel I'm able to help out with a review here.

[tchaikov]

thanks @alimaredia !

@cbodley do you happen to know who can help review debian packaging changes in our project?

[cbodley]

given the ack from Thomas, i'm happy to approve as long as this goes through qa. is there any additional testing we should do to validate the behavior against systemd?

[tchaikov]

given the ack from Thomas, i'm happy to approve as long as this goes through qa. is there any additional testing we should do to validate the behavior against systemd?

i installed the packages built with this change in a container, and uninstalled them without errors. also, there are a lot of proxmox users using the postrm script equivalent to the one generated with this change, so they are practically testing the change. i think it should suffice as a proof that this change is correct.

[Naveenaidu]

RADOS Approved: https://tracker.ceph.com/issues/74325#note-6