Writing System V init scripts for Red Hat Linux

    All System V init scripts are named /etc/rc.d/init.d/<servicename> where <servicename> is the name of the service. There must be no ".init" suffix.

Sample Script:

#!/bin/bash
#
# /etc/rc.d/init.d/<servicename>
#
# <description of the *service*>
# <any general comments about this init script>
#
# <tags -- see below for tag definitions. *Every line* from the top
# of the file to the end of the tags section must begin with a #
# character. After the tags section, there should be a blank line.
# This keeps normal comments in the rest of the file from being
# mistaken for tags, should they happen to fit the pattern.>

# Source function library.
. /etc/rc.d/init.d/functions

<define any local shell functions used by the code that follows>

case "$1" in
	start)
		echo -n "Starting <servicename> services: "
		<start daemons, perhaps with the daemon function>
		touch /var/lock/subsys/<servicename>
	;;
	stop)
		echo -n "Shutting down <servicename> services: "
		<stop daemons, perhaps with the killproc function>
		rm -f /var/lock/subsys/<servicename>
	;;
	status)
		<report the status of the daemons in free-form format,
		perhaps with the status function>
	;;
	restart)
		<restart the daemons, normally with $0 stop; $0 start>
	;;
	reload)
		<cause the service configuration to be reread, either with
		kill -HUP or by restarting the daemons, possibly with
		$0 stop; $0 start>
	;;
	probe)
		<optional. If it exists, then it should determine whether
		or not the service needs to be restarted or reloaded (or
		whatever) in order to activate any changes in the configuration
		scripts. It should print out a list of commands to give to
		$0; see the description under the probe tag below.>
	;;
	*)
		echo "Usage: <servicename> {start|stop|status|reload|restart[|probe]"
		exit 1
	;;
esac

    Notes: the restart and reload functions may be (and commonly are) combined into one test, vis:

• restart | reload)

    You are not prohibited from adding other commands; list all commands which you intend to be used interactively to the usage message.

Functions in /etc/rc.d/init.d/functions

daemon [+/-nicelevel] program [arguments] [&]

    Starts a daemon, if it is not already running. Does other useful things like keeping the daemon from dumping core if it terminates unexpectedly.

killproc program [signal]

    Sends a signal to the program; by default it sends a SIGTERM, and if the process doesn't die, it sends a SIGKILL a few seconds later.

    It also tries to remove the pidfile, if it finds one.

pidofproc program

    Tries to find the pid of a program; checking likely pidfiles, using the pidof program, or even using ps. Used mainly from within other functions in this file, but also available to scripts.

status program

    Prints status information. Assumes that the program name is the same as the servicename.

Tags.

# chkconfig: <startlevellist> <startpriority> <endpriority>

    Required. <startlevellist> is a list of levels in which the service should be started by default. <startpriority> and <endpriority> are priority numbers. For example: # chkconfig: 2345 20 80 Read 'man chkconfig' for more information.

    Unless there is a VERY GOOD, EXPLICIT reason to the contrary, the <endpriority> should be equal to 100 - <startpriority>

# description: <multi-line description of service>

    Required. Several lines of description, continued with '\' characters. The initial comment and following whitespace on the following lines is ignored.

# description[ln]: <multi-line description of service in the language \ # ln, whatever that is>

    Optional. Should be the description translated into the specified language.

# processname:

    Optional, multiple entries allowed. For each process name started by the script, there should be a processname entry. For example, the samba service starts two daemons:
# processname: smdb
# processname: nmdb

# config:

    Optional, multiple entries allowed. For each static config file used by the daemon, use a single entry. For example:
# config: /etc/httpd/conf/httpd.conf
# config: /etc/httpd/conf/srm.conf

    Optionally, if the server will automatically reload the config file if it is changed, you can append the word "autoreload" to the line:
# config: /etc/foobar.conf autoreload

# pidfile:

    Optional, multiple entries allowed. Use just like the config entry, except that it points at pidfiles. It is assumed that the pidfiles are only updated at process creation time, and not later. The first line of this file should be the ASCII representation of the PID; a terminating newline is optional. Any lines other than the first line are not examined.

# probe: true

    Optional, used IN PLACE of processname, config, and pidfile. If it exists, then a proper reload-if-necessary cycle may be acheived by running these commands:

command=$(/etc/rd.d/init.d/SCRIPT probe)
[ -n "$command" ] && /etc/rc.d/init.d/SCRIPT $command

    Scripts that need to do complex processing could, as an example, return "run /var/tmp/<servicename.probe.$$" and implement a "run" command which would execute the named script and then remove it.