RHEL: Services basic management

RHEL: Services basic management - chkconfig

# Tested on RHEL 5 & 6

# If one of "on", "off", "reset", or "resetpriorities" is specified after the service name,
# 'chkconfig' command 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 on/off state for all runlevels for the service to whatever is
# specified in the init script in question, while the "resetpriorities" flag resets the
# start/stop priorities for the service to whatever is specifed in the init script.

# By default, the "on" and "off" options affect only runlevels 2, 3, 4, and 5, while "reset"
# and "resetpriorities" 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 restart an already-started service, and will not
# re-stop a service that is not running.

# 'chkconfig' also can manage xinetd scripts via the means of xinetd.d configuration files.
# Note that only the "on", "off", and "--list" commands are supported for xinetd.d services.

# For example, random.init has these three lines in its header:

# 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.

# ------------------------------------------------------------------------------------------
# Creating a service
# ------------------------------------------------------------------------------------------

# To create a new service on RHEL we have to run following command:

root@<server>:/#> chkconfig --add <service_name>

# Requirements:
# - An executable script must exit under /etc/init.d with the name <service_name>
# - As already pointed, this script must contain a valid header:

      #!/bin/bash

      # Start script for XXXXX service

      # chkconfig: - 85 15
      # description: XXXXX
      # processname: <nombre_proceso>
      # pidfile: /var/run/<nombre_proceso>.pid
      # config:

# "chkconfig --add" creates, if they don't exist already, the "stop" links to service
# script. For instance:

root@<server>:/#> find /etc -name "*<service_name>*"
   /etc/rc.d/init.d/<service_name>
   /etc/rc.d/rc0.d/K15<service_name>
   /etc/rc.d/rc1.d/K15<service_name>
   /etc/rc.d/rc2.d/K15<service_name>
   /etc/rc.d/rc3.d/K15<service_name>
   /etc/rc.d/rc4.d/K15<service_name>
   /etc/rc.d/rc5.d/K15<service_name>
   /etc/rc.d/rc6.d/K15<service_name>

# ------------------------------------------------------------------------------------------
# Verifying service status
# ------------------------------------------------------------------------------------------

# Once service has been created we can check status of run levels by running following command:

root@<server>:/#> chkconfig --list <service_name>
   <service_name>          0:off   1:off   2:off   3:off   4:off   5:off   6:off

# ------------------------------------------------------------------------------------------
# Customizing run levels
# ------------------------------------------------------------------------------------------

# To customize service activation, via the different startup levels, we use
# "chkconfig --level NNNN <service_name> on" command where NNNN is the level number(s)
# where our service will be enabled

root@<server>:/#> chkconfig --level 2345 <service_name> on

root@<server>:/#> chkconfig --list <service_name>                  # Check
   <service_name>          0:off   1:off   2:on    3:on    4:on    5:on    6:off

root@<server>:/#> find /etc -name "*<service_name>*"               # Check
   /etc/rc.d/init.d/<service_name>
   /etc/rc.d/rc0.d/K15<service_name>
   /etc/rc.d/rc1.d/K15<service_name>
   /etc/rc.d/rc2.d/S15<service_name>
   /etc/rc.d/rc3.d/S15<service_name>
   /etc/rc.d/rc4.d/S15<service_name>
   /etc/rc.d/rc5.d/S15<service_name>
   /etc/rc.d/rc6.d/K15<service_name>

root@<server>:/#> chkconfig --level 45 <service_name> off

root@<server>:/#> chkconfig --list <service_name>                  # Check
   <service_name>          0:off   1:off   2:on    3:on    4:off    5:off    6:off

root@<server>:/#> find /etc -name "*<service_name>*"               # Check
   /etc/rc.d/init.d/<service_name>
   /etc/rc.d/rc0.d/K15<service_name>
   /etc/rc.d/rc1.d/K15<service_name>
   /etc/rc.d/rc2.d/S15<service_name>
   /etc/rc.d/rc3.d/S15<service_name>
   /etc/rc.d/rc4.d/K15<service_name>
   /etc/rc.d/rc5.d/K15<service_name>
   /etc/rc.d/rc6.d/K15<service_name>

# ------------------------------------------------------------------------------------------
# Removing service
# ------------------------------------------------------------------------------------------

# To remove start/stop links to service script:

root@<server>:/#> chkconfig --del <service_name>

root@<server>:/#> chkconfig --list <service_name>                  # Check
   service <service_name> supports chkconfig, but is not referenced in any runlevel (run 'chkconfig --add <service_name>')

root@<server>:/#> find /etc -name "*<service_name>*"               # Check
   /etc/rc.d/init.d/<service_name>

# ------------------------------------------------------------------------------------------
# Managing service
# ------------------------------------------------------------------------------------------

# From now on, and depending on script design, service can be managed using "service" command

root@<server>:/#> service <service_name> [ start | stop | restart | ... ]

# ------------------------------------------------------------------------------------------
# Example: 'bluetooth' service
# ------------------------------------------------------------------------------------------

root@<server>:/#> ll /etc/init.d/bluetooth
-rwxr-xr-x 1 root root 1477 Jul 9 2008 /etc/init.d/bluetooth

root@<server>:/#> cat /etc/init.d/bluetooth
   #!/bin/sh
   #
   # bluetooth:    Start/stop bluetooth services
   #
   # chkconfig:    2345 25 90
   # description: Bluetooth services for service discovery, authentication, \
   #               Human Interface Devices, etc.
   #

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

   UART_CONF="/etc/bluetooth/uart"

   [ -e /etc/sysconfig/bluetooth ] && . /etc/sysconfig/bluetooth

   start_uarts()
   {
           [ -f $UART_CONF ] || return
           grep -v '^#' $UART_CONF | while read i; do
                   /usr/sbin/hciattach $i
           done
   }

   stop_uarts()
   {
           killproc hciattach > /dev/null 2>&1
   }

   start()
   {
           echo -n $"Starting Bluetooth services:"
           daemon /usr/sbin/hcid
           touch /var/lock/subsys/hcid
           daemon /usr/sbin/sdpd
           touch /var/lock/subsys/sdpd
           [ "$HID2HCI_ENABLE" = "true" ] && hid2hci --tohci > /dev/null 2>&1 || :
           start_uarts
           rfcomm bind all
           touch /var/lock/subsys/bluetooth
           echo ""
   }

   stop()
   {
           echo -n "Stopping Bluetooth services:"
           stop_uarts
           rfcomm release all
           [ "$HID2HCI_UNDO" = "true" ] && hid2hci --tohid > /dev/null 2>&1 || :
           killproc sdpd
           rm -f /var/lock/subsys/sdpd
           killproc hcid
           rm -f /var/lock/subsys/hcid
           rm -f /var/lock/subsys/bluetooth
           echo ""
   }

   case "$1" in
     start)
           start
           ;;
     stop)
           stop
           ;;
     restart|reload)
           stop
           start
           ;;
     condrestart)
           [ -e /var/lock/subsys/bluetooth ] && (stop; start)
           ;;
     status)
           status hcid
           status sdpd
           ;;
     *)
           echo $"Usage: $0 {start|stop|status|restart|reload|condrestart}"
           exit 1
           ;;
   esac

   exit 0

root@<server>:/#> chkconfig --list bluetooth
   bluetooth       0:off   1:off   2:on    3:on    4:on    5:on    6:off

root@<server>:/#> find /etc -name "*bluetooth*"
   /etc/udev/rules.d/bluetooth.rules
   /etc/sysconfig/bluetooth
   /etc/bluetooth
   /etc/rc.d/init.d/bluetooth
   /etc/rc.d/rc6.d/K90bluetooth
   /etc/rc.d/rc4.d/S25bluetooth
   /etc/rc.d/rc5.d/S25bluetooth
   /etc/rc.d/rc2.d/S25bluetooth
   /etc/rc.d/rc1.d/K90bluetooth
   /etc/rc.d/rc3.d/S25bluetooth
   /etc/rc.d/rc0.d/K90bluetooth

root@<server>:/#> service bluetooth
   Usage: /etc/init.d/bluetooth {start|stop|status|restart|reload|condrestart}

root@<server>:/#> service bluetooth status
   hcid dead but subsys locked
   sdpd (pid 5406) is running...