cpack: add apt package manager prerm script

[shaerpour]

Description

When we install packages with apt, rpm or other package managers, some bash scripts with (prerm, preinst, postrm and postinst) extensions would be execute (if exists) that do some tasks like copy config files, create directories etc before or after unpacking package so the main program can run in the better environment.

Issue

If remove and purge package without stop (and | or) disable it, OS still shows the service is running and can cause issues after rebooting.

Added feature

In this branch, the prerm script is added to prevent those issues. (Built and tested on ubuntu:20.04)

[cosmo0920]

Shouldn't we check whether service or systemctl command is effective on the Debian box?

[shaerpour]

Sure! I will test it on Debian 11 and 12 and reply back with results.

[shaerpour]

Tests have been successfully done on debian bullseye and bookworm versions.
After Debian 8 systemd is the default init system for debian (Debian Reference) so systemctl would not make any issues.

[cosmo0920]

Sounds great. So, we shouldn't consider the outdated Debian system. Let's leave as-is.

[aminvakil]

This should be investigated more whether this is the right choice to do or not, take fail2ban.prerm package which has been downloaded and installed from https://github.com/fail2ban/fail2ban/releases/download/1.0.2/fail2ban_1.0.2-1.upstream1_all.deb on Debian 10 Buster for example:

#!/bin/sh
set -e
# Automatically added by dh_installinit/13.3.4
if [ -x "/etc/init.d/fail2ban" ] && [ "$1" = remove ]; then
        invoke-rc.d fail2ban stop || exit 1
fi
# End automatically added section

# Automatically added by dh_python3
if which py3clean >/dev/null 2>&1; then
        py3clean -p fail2ban 
else
        dpkg -L fail2ban | perl -ne 's,/([^/]*)\.py$,/__pycache__/\1.*, or next; unlink $_ or die $! foreach glob($_)'
        find /usr/lib/python3/dist-packages/ -type d -name __pycache__ -empty -print0 | xargs --null --no-run-if-empty rmdir
fi

# End automatically added section

First it uses /bin/sh instead of /bin/bash and it seems some stuff would be handled by dh_installinit which will be automatically added to prerm files of package.

So maybe it's better to rely on debscripts scripts to run these stuff instead of executing systemctl disable and systemctl stop manually.

[aminvakil]

Suggested change

	#!/bin/bash
	#!/bin/sh

[aminvakil]

Also netfilter-persistent.prem on Debian 10 Buster and Debian 11 Bullseye:

Debian 10 Buster:

#!/bin/sh
set -e
# Automatically added by dh_installinit/12.1.1
if [ -x "/etc/init.d/netfilter-persistent" ] && [ "$1" = remove ]; then
        invoke-rc.d netfilter-persistent stop || exit 1
fi
# End automatically added section

Debian 11 Bullseye:

#!/bin/sh
set -e
# Automatically added by dh_installsystemd/13.3.3
if [ -d /run/systemd/system ] && [ "$1" = remove ]; then
        deb-systemd-invoke stop 'netfilter-persistent.service' >/dev/null || true
fi
# End automatically added section
# Automatically added by dh_installinit/13.3.3
if [ -x "/etc/init.d/netfilter-persistent" ] && [ "$1" = remove ]; then
        invoke-rc.d --skip-systemd-native netfilter-persistent stop || exit 1
fi
# End automatically added section

This is more suggesting that these stuff should be handled using debhelper itself.