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#!/usr/bin/perl
# vim:ts=4:sw=4:expandtab
# © 2013 Michael Stapelberg <stapelberg@debian.org>
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#     * Redistributions of source code must retain the above copyright
#       notice, this list of conditions and the following disclaimer.
#
#     * Redistributions in binary form must reproduce the above copyright
#       notice, this list of conditions and the following disclaimer in the
#       documentation and/or other materials provided with the distribution.
#
#     * Neither the name of Michael Stapelberg nor the
#       names of contributors may be used to endorse or promote products
#       derived from this software without specific prior written permission.
# .
# THIS SOFTWARE IS PROVIDED BY Michael Stapelberg ''AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL Michael Stapelberg BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

=head1 NAME

deb-systemd-invoke - wrapper around systemctl, respecting policy-rc.d

=head1 SYNOPSIS

B<deb-systemd-invoke> start|stop|restart S<I<unit file> ...>

=head1 DESCRIPTION

B<deb-systemd-invoke> is a Debian-specific helper script which asks
/usr/sbin/policy-rc.d before performing a systemctl call.

B<deb-systemd-invoke> is intended to be used from maintscripts to start
systemd unit files. It is specifically NOT intended to be used interactively by
users. Instead, users should run systemd and use systemctl, or not bother about
the systemd enabled state in case they are not running systemd.

=cut

use strict;
use warnings;

if (@ARGV < 2) {
    print STDERR "Syntax: $0 <action> <unit file> [<unit file> ...]\n";
    exit 1;
}

my $policyhelper = '/usr/sbin/policy-rc.d';
my @units = @ARGV;
my $action = shift @units;
if (-x $policyhelper) {
    for my $unit (@units) {
        system(qq|$policyhelper $unit "$action"|);

        # 0 or 104 means run
        # 101 means do not run
        my $exitcode = ($? >> 8);
        if ($exitcode == 101) {
            print STDERR "$policyhelper returned 101, not running '" . join(' ', @ARGV) . "'\n";
            exit 0;
        } elsif ($exitcode != 104 && $exitcode != 0) {
            print STDERR "deb-systemd-invoke only supports $policyhelper return codes 0, 101, and 104!\n";
            print STDERR "Got return code $exitcode, ignoring.\n";
        }
    }
}

# If the job is disabled and is not currently running, the job is not started or restarted.
# However, if the job is disabled but has been forced into the running state, we *do* stop
# and restart it since this is expected behaviour for the admin who forced the start.
# We don't autostart static units either.
if ($action eq "start" || $action eq "restart") {
    my $global_exit_code = 0;
    my @start_units = ();
    for my $unit (@units) {
        my $unit_installed = 0;
        my $enabled_output = `/bin/systemctl is-enabled -- '$unit'`;
        # matching enabled and enabled-runtime as an installed non static unit
        if ($enabled_output =~ /enabled/) {
            $unit_installed = 1;
        }
        system('/bin/systemctl', '--quiet', 'is-active', '--', $unit);
        my $unit_active = $?>>8 == 0 ? 1 : 0;
        if (!$unit_installed && $action eq "start") {
            print STDERR "$unit is a disabled or a static unit, not starting it.\n";
        } elsif (!$unit_installed && !$unit_active && $action eq "restart") {
            print STDERR "$unit is a disabled or a static unit not running, not starting it.\n";
        }
        else {
            push @start_units, $unit;
        }
    }
    if (@start_units) {
        exec('/bin/systemctl', $action, @start_units) or die("Could not execute systemctl: $!");
    }
    exit(0);
} else {
    exec '/bin/systemctl', @ARGV;
}