Added Debian Sysvinit support

Makefile

@@ -4,6 +4,7 @@ PREFIX ?= /usr
 INITCPIO ?= false
 SYSTEMD ?= true
 OPENRC ?= false
+SYSVINIT ?= false
 
 BOOT_DIR_DEBIAN ?= /boot/grub
 BOOT_DIR_FEDORA ?= /boot/grub2
@@ -64,6 +65,10 @@ install:
 		install -Dm744 grub-btrfsd.initd "$(DESTDIR)/etc/init.d/grub-btrfsd"; \
 		install -Dm644 grub-btrfsd.confd "$(DESTDIR)/etc/conf.d/grub-btrfsd"; \
 	 fi
+	@if test "$(SYSVINIT)" = true; then \
+		echo "Installing sysvinit init.d file"; \
+		install -Dm755 grub-btrfsd.sysvinit.initd "$(DESTDIR)/etc/init.d/grub-btrfsd"; \
+	 fi
 	@# Arch Linux like distros only :
 	@if test "$(INITCPIO)" = true; then \
 		echo "Installing initcpio hook"; \

README.md

@@ -274,6 +274,51 @@ After that, the daemon should be restarted with:
 sudo rc-service grub-btrfsd restart
 ```
 
+- - -
+#### grub-btrfsd Sysvinit instructions
+The sysvinit grub-btrfsd script is designed for Debian and
+Debian-based distributions using sysvinit (Devuan, MX Linux, etc). It depends on Linux
+Standards Base (LSB) init functions which are located at
+`/lib/lsb/init-functions` on Debian and Debian-derivatives. These functions may be located in a
+different directory in other distributions using sysvinit, and the
+functions contained therein may differ from those called in the script.
+
+To start the daemon run:
+```bash
+sudo service grub-btrfsd start
+```
+
+To activate it during system startup, run:
+```bash
+sudo update-rc.d grub-btrfsd defaults
+```
+
+##### 💼 Snapshots not in `/.snapshots` for Sysvinit
+By default the daemon is watching the directory `/.snapshots`. If the daemon should watch a different directory, it can be edited by passing different arguments to it.
+Arguments are passed to grub-btrfsd via `DAEMON_ARGS` and `SNAPSHOTS`
+variables in the script `/etc/init.d/grub-btrfsd`.
+The variable `SNAPSHOTS` defines the path the daemon will monitor for
+snapshots.
+
+After editing, the applicable portion of the file should look like this:
+
+``` bash
+SNAPSHOTS="/.snapshots" # Snapper in the root directory
+# SNAPSHOTS="/run/timeshift/backup/timeshift-btrfs/snapshots" # Timeshift < v22.06
+
+## Optional arguments to run with the daemon
+# Append options to this like this:
+# DAEMON_ARGS="--syslog --timeshift-auto --verbose"
+# Possible options are:
+# -t, --timeshift-auto  Automatically detect Timeshifts snapshot directory for timeshift >= 22.06
+# -o, --timeshift-old   Look for snapshots in directory of Timeshift <v22.06 (requires --timeshift-auto)
+# -l, --log-file        Specify a logfile to write to
+# -v, --verbose         Let the log of the daemon be more verbose
+# -s, --syslog          Write to syslog
+
+DAEMON_ARGS="--syslog"
+```
+
 ##### 🔒 Snapshots on LUKS encrypted devices
 By default, grub-btrfs generates entries that does not load modules for dealing with encrypted devices.
 Enable the `GRUB_BTRFS_ENABLE_CRYPTODISK` variable in `/etc/default/grub-btrfs/config` to load said modules and then execute the steps to mount encrypted root after selecting the snapshot.

grub-btrfsd.sysvinit.initd

@@ -0,0 +1,102 @@
+#!/bin/sh
+### BEGIN INIT INFO
+# Provides:          grub-btrfsd
+# Required-Start:    $local_fs $syslog
+# Required-Stop:     $local_fs $syslog
+# Default-Start:     2 3 4 5
+# Default-Stop:      0 1 6
+# Short-Description: Regenerate grub-btrfs.cfg
+# Description:       Monitors btrfs snapshots created with snapper
+#                    or Timeshift and automatically regenerates
+#                    grub-btrfs.cfg.
+### END INIT INFO
+
+PATH=/usr/sbin:/usr/bin:/sbin:/bin
+
+DESC="grub-btrfs snapshot daemon"
+NAME=grub-btrfsd
+DAEMON=/usr/bin/$NAME
+PIDFILE=/run/$NAME.pid
+
+SCRIPTNAME=/etc/init.d/$NAME
+
+SNAPSHOTS="/.snapshots" # Snapper in the root directory
+# SNAPSHOTS="/run/timeshift/backup/timeshift-btrfs/snapshots" # Timeshift < v22.06
+
+## Optional arguments to run with the daemon
+# Append options to this like this:
+# DAEMON_ARGS="--syslog --timeshift-auto --verbose"
+# Possible options are:
+# -t, --timeshift-auto  Automatically detect Timeshifts snapshot directory for timeshift >= 22.06
+# -o, --timeshift-old   Look for snapshots in directory of Timeshift <v22.06 (requires --timeshift-auto)
+# -l, --log-file        Specify a logfile to write to
+# -v, --verbose         Let the log of the daemon be more verbose
+# -s, --syslog          Write to syslog
+
+DAEMON_ARGS="--syslog" # Snapper
+# DAEMON_ARGS="--syslog --timeshift-auto --verbose" # Timeshift >= 22.06
+
+# Exit if the package is not installed
+[ -x "$DAEMON" ] || exit 0
+
+# Load LSB init functions.
+# This is the path for Debian and Devuan, may vary on other distributions.
+. /lib/lsb/init-functions
+
+do_start() {
+    start-stop-daemon \
+        --start \
+        --background \
+        --make-pidfile \
+        --pidfile "$PIDFILE" \
+        --exec "$DAEMON" -- \
+        $DAEMON_ARGS \
+        "$SNAPSHOTS"
+}
+
+do_stop() {
+    start-stop-daemon \
+        --stop \
+        --quiet \
+        --retry=TERM/30/KILL/5 \
+        --pidfile "$PIDFILE"
+}
+
+case "$1" in
+    start)
+        log_daemon_msg "Starting $DESC" "$NAME"
+        if do_start; then
+            log_end_msg 0
+        else
+            log_end_msg 1
+        fi
+        ;;
+    stop)
+        log_daemon_msg "Stopping $DESC" "$NAME"
+        if do_stop; then
+            log_end_msg 0
+        else
+            log_end_msg 1
+        fi
+        ;;
+    restart|force-reload)
+        log_daemon_msg "Restarting $DESC" "$NAME"
+        do_stop
+        sleep 1
+        if do_start; then
+            log_end_msg 0
+        else
+            log_end_msg 1
+        fi
+        ;;
+    status)
+        status_of_proc -p "$PIDFILE" "$DAEMON" "$NAME"
+        exit $?
+        ;;
+    *)
+        echo "Usage: $SCRIPTNAME {start|stop|restart|force-reload|status}"
+        exit 2
+        ;;
+esac
+
+exit 0