chkconfig — Linux / Unix Command

Check RC configurations on Sysvinit Linux systems

The command 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.

The chkconfig tool and the RC files system that it works with are part of the traditional Sysvinit system. Most Linux distributions rely on the newer Systemd init system. Unless you've chosen a distribution that still relies on Sysvinit, this guide does not apply to your system.

Synopsis

Chkconfig updates and queries runlevel information for system services. The command takes one of the following forms:

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

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 approach leaves in a single location all of the configuration information regarding what services init starts.

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 runs 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 queries an alternative runlevel rather than the current one.

If one of onoff, 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 specifies which runlevels are affected.

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

The command accepts several optional flags:

  • --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 service has either a start or a kill entry in every runlevel. If any runlevel is missing such an entry, chkconfig creates the appropriate entry as specified by the default values in the init script. Note that default 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 symbolic links 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 line tells chkconfig what runlevels the service should be started in by default, as well as the start and stop priority levels. If the service should not, by default, be started in any runlevels, a hyphen should be used in place of the runlevels list. The second line contains a description for the service and may be extended across multiple 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 file 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.