From: Petter Reinholdtsen Date: Sat, 2 Nov 2013 21:30:56 +0000 (+0000) Subject: New post. X-Git-Url: https://pere.pagekite.me/gitweb/homepage.git/commitdiff_plain/50a18b7793d1cd69f1ec69f75567f6271d540cdd?ds=sidebyside New post. --- diff --git a/blog/data/2013-11-02-debian-init-d-script.txt b/blog/data/2013-11-02-debian-init-d-script.txt new file mode 100644 index 0000000000..d760aac9b9 --- /dev/null +++ b/blog/data/2013-11-02-debian-init-d-script.txt @@ -0,0 +1,193 @@ +Title: Debian init.d boot script example for rsyslog +Tags: english, debian +Date: 2013-11-02 22:40 + +

If one of the points of switching to a new init system in Debian is +to get rid of huge +init.d scripts, I doubt we need to switch away from sysvinit and +init.d scripts at all. Here is an example init.d script, ie a rewrite +of /etc/init.d/rsyslog:

+ +

+#!/lib/init/init-d-script
+### BEGIN INIT INFO
+# Provides:          rsyslog
+# Required-Start:    $remote_fs $time
+# Required-Stop:     umountnfs $time
+# X-Stop-After:      sendsigs
+# Default-Start:     2 3 4 5
+# Default-Stop:      0 1 6
+# Short-Description: enhanced syslogd
+# Description:       Rsyslog is an enhanced multi-threaded syslogd.
+#                    It is quite compatible to stock sysklogd and can be 
+#                    used as a drop-in replacement.
+### END INIT INFO
+DESC="enhanced syslogd"
+DAEMON=/usr/sbin/rsyslogd
+

+ +

Pretty minimalistic to me... For the record, the original sysv-rc +script was 126 lines, and the above is just 15 lines, most of the meta +info/comments.

+ +

How to do this, you ask? Well, one create a new script +/lib/init/init-d-script looking something like this: + +

+#!/bin/sh
+
+# Define LSB log_* functions.
+# Depend on lsb-base (>= 3.2-14) to ensure that this file is present
+# and status_of_proc is working.
+. /lib/lsb/init-functions
+
+#
+# Function that starts the daemon/service
+
+#
+do_start()
+{
+	# Return
+	#   0 if daemon has been started
+	#   1 if daemon was already running
+	#   2 if daemon could not be started
+	start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON --test > /dev/null \
+		|| return 1
+	start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON -- \
+		$DAEMON_ARGS \
+		|| return 2
+	# Add code here, if necessary, that waits for the process to be ready
+	# to handle requests from services started subsequently which depend
+	# on this one.  As a last resort, sleep for some time.
+}
+
+#
+# Function that stops the daemon/service
+#
+do_stop()
+{
+	# Return
+	#   0 if daemon has been stopped
+	#   1 if daemon was already stopped
+	#   2 if daemon could not be stopped
+	#   other if a failure occurred
+	start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE --name $NAME
+	RETVAL="$?"
+	[ "$RETVAL" = 2 ] && return 2
+	# Wait for children to finish too if this is a daemon that forks
+	# and if the daemon is only ever run from this initscript.
+	# If the above conditions are not satisfied then add some other code
+	# that waits for the process to drop all resources that could be
+	# needed by services started subsequently.  A last resort is to
+	# sleep for some time.
+	start-stop-daemon --stop --quiet --oknodo --retry=0/30/KILL/5 --exec $DAEMON
+	[ "$?" = 2 ] && return 2
+	# Many daemons don't delete their pidfiles when they exit.
+	rm -f $PIDFILE
+	return "$RETVAL"
+}
+
+#
+# Function that sends a SIGHUP to the daemon/service
+#
+do_reload() {
+	#
+	# If the daemon can reload its configuration without
+	# restarting (for example, when it is sent a SIGHUP),
+	# then implement that here.
+	#
+	start-stop-daemon --stop --signal 1 --quiet --pidfile $PIDFILE --name $NAME
+	return 0
+}
+
+SCRIPTNAME=$1
+scriptbasename="$(basename $1)"
+echo "SN: $scriptbasename"
+if [ "$scriptbasename" != "init-d-library" ] ; then
+    script="$1"
+    shift
+    . $script
+else
+    exit 0
+fi
+
+NAME=$(basename $DAEMON)
+PIDFILE=/var/run/$NAME.pid
+
+# Exit if the package is not installed
+#[ -x "$DAEMON" ] || exit 0
+
+# Read configuration variable file if it is present
+[ -r /etc/default/$NAME ] && . /etc/default/$NAME
+
+# Load the VERBOSE setting and other rcS variables
+. /lib/init/vars.sh
+
+case "$1" in
+  start)
+	[ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
+	do_start
+	case "$?" in
+		0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
+		2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
+	esac
+	;;
+  stop)
+	[ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME"
+	do_stop
+	case "$?" in
+		0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
+		2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
+	esac
+	;;
+  status)
+	status_of_proc "$DAEMON" "$NAME" && exit 0 || exit $?
+	;;
+  #reload|force-reload)
+	#
+	# If do_reload() is not implemented then leave this commented out
+	# and leave 'force-reload' as an alias for 'restart'.
+	#
+	#log_daemon_msg "Reloading $DESC" "$NAME"
+	#do_reload
+	#log_end_msg $?
+	#;;
+  restart|force-reload)
+	#
+	# If the "reload" option is implemented then remove the
+	# 'force-reload' alias
+	#
+	log_daemon_msg "Restarting $DESC" "$NAME"
+	do_stop
+	case "$?" in
+	  0|1)
+		do_start
+		case "$?" in
+			0) log_end_msg 0 ;;
+			1) log_end_msg 1 ;; # Old process is still running
+			*) log_end_msg 1 ;; # Failed to start
+		esac
+		;;
+	  *)
+		# Failed to stop
+		log_end_msg 1
+		;;
+	esac
+	;;
+  *)
+	echo "Usage: $SCRIPTNAME {start|stop|status|restart|force-reload}" >&2
+	exit 3
+	;;
+esac
+
+:
+

+ +

It is based on /etc/init.d/skeleton, and could be improved quite a +lot. I did not try hard to optimize it nor make it more robust.

+ +

A better argument for switching init system in Debian than reducing +the size of init scripts (which is a good thing to do anyway), is to +get boot system that is able to handle the kernel events sensibly and +robustly, and do not depend the boot to run sequentially. The boot +and the kernel have not behaved sequentially in year.