How to control services in linux with chkconfig

Linux / Unix Command: chkconfig

chkconfig - updates and queries runlevel information for system services:

chkconfig --list [name]
chkconfig --add name
chkconfig --del name
chkconfig [--level levels] name <on|off|reset>
chkconfig [--level levels] name

DESCRIPTION

chkconfig provides a simple command-line tool for maintaining the /etc/rc[0-6].d directory hierarchy by relieving system administrators of the task of directly manipulating the numerous symbolic links in those directories.

This implementation of chkconfig was inspired by the chkconfig command present in the IRIX operating system. Rather than maintaining configuration information outside of the /etc/rc[0-6].d hierarchy, however, this version directly manages the symlinks in /etc/rc[0-6].d. This leaves all of the configuration information regarding what services init
starts in a single location. chkconfig has five distinct functions: adding new services for
management, removing services from management, listing the current startup information for services, changing the startup information for services, and checking the startup state of a particular service. When chkconfig is run without any options, it displays usage
information. If only a service name is given, it checks to see if the service is configured to be started in the current runlevel. If it is, chkconfig returns true; otherwise it returns false. The
--level option may be used to have chkconfig query an alternative runlevel rather than the current one. If one of on, off, or reset is specified after the service name, chkconfig changes the startup information for the specified service. The on and off flags cause the service
to be started or stopped, respectively, in the runlevels being changed. The reset flag resets the startup information for the service to whatever is specified in the init script in question.

By default, the on and off options affect only runlevels 2, 3, 4, and 5, while reset affects all of the runlevels. The --level option may be used to specify which runlevels are affected.

Note that for every service, each runlevel has either a start script or a stop script. When switching runlevels, init will not re-start an already-started service, and will not re-stop a service that is not running.

OPTIONS

--level levels

Specifies the run levels an operation should pertain to. It is given as a string of numbers from 0 to 7. For example, --level 35 specifies runlevels 3 and 5.

--add name

This option adds a new service for management by chkconfig.When a new service is added, chkconfig ensures that the servicehas either a start or a kill entry in every runlevel. If any runlevel is missing such an entry, chkconfig creates the appropriate entryas specified by the default values in the init script. Note thatdefault entries in LSB-delimited 'INIT INFO' sections take precedence over the default runlevels in the initscript.

--del name

The service is removed from chkconfig management, and any symboliclinks in /etc/rc[0-6].d which pertain to it are removed.

--list name

This option lists all of the services which chkconfig knows about, and whether they are stopped or started in each runlevel. If name is specified, information in only display about service name.

RUNLEVEL FILES

Each service which should be manageable by chkconfig needs two or more commented lines added to its init.d script. The first linetells chkconfig what runlevels the service should be started in by default, as well as the start and stop priority levels. If the serviceshould not, by default, be started in any runlevels, a - should be used in place of the runlevels list. The second line contains a description for the service, and may be extended acrossmultiple lines with backslash continuation.

For example, random.init has these three lines:

# chkconfig: 2345 20 80
# description: Saves and restores system entropy pool for \
#              higher quality random number generation.

This says that the random script should be started in levels 2, 3, 4, and 5, that its start priority should be 20, and that its stop priority should be 80. You should be able to figure out what the description says; the \ causes the line to be continued. The
extra space in front of the line is ignored.

For instance take a look on service configuration to run tomcat:

#startup script for Jakarta Tomcat
#
# chkconfig: 345 84 16
# description: Jakarta Tomcat Java Servlet/JSP Container

TOMCAT_HOME=/usr/local/bin/apache-tomcat-6.0.16
TOMCAT_START=/usr/local/bin/apache-tomcat-6.0.16/bin/startup.sh
TOMCAT_STOP=/usr/local/bin/apache-tomcat-6.0.16/bin/shutdown.sh
TOMCAT_RUN=/usr/local/bin/apache-tomcat-6.0.16/bin/catalina.sh
#Necessary environment variables
export CATALINA_HOME=/usr/local/bin/apache-tomcat-6.0.16

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

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0

#Check for tomcat script
if [ ! -f $TOMCAT_HOME/bin/catalina.sh ]
then
 echo "Tomcat not available..."
 exit
fi

start() {
 echo -n "Starting Tomcat: "
 su - root -c $TOMCAT_START
 echo
 touch /var/lock/subsys/tomcatd
# We may need to sleep here so it will be up for apache
#    sleep 5
#Instead should check to see if apache is up by looking for http.pid
}
run() {
 echo -n "Starting Tomcat: "
 su - root -c $TOMCAT_START
 echo
 touch /var/lock/subsys/tomcatd
# We may need to sleep here so it will be up for apache
#    sleep 5
#Instead should check to see if apache is up by looking for http.pid
}

stop() {
 echo -n $"Shutting down Tomcat: "
 su - root -c $TOMCAT_STOP
 rm -f /var/lock/subsys/tomcatd.pid
 echo
}

status() {
 ps ax --width=1000 | grep "[o]rg.apache.catalina.startup.Bootstrap
start" | awk '{printf $1 " "}' | wc | awk '{print $2}' > /tmp/tomcat_process_count.txt
read line < /tmp/tomcat_process_count.txt if [ $line -gt 0 ]; then     echo -n "tomcatd ( pid "     ps ax --width=1000 | grep "[o]rg.apache.catalina.startup.Bootstrap start" | awk '{printf $1 " "}'     echo -n ") is running..." else     echo -n "Tomcat is stopped" fi }  case "$1" in     start)         start         ;;       run)         run         ;;       stop)         stop         ;;      restart)         stop         sleep 3         start         ;;      status)         status         ;;      *)         echo "Usage: tomcatd {start|stop|restart|status}"      exit 1 esac