Ubuntu Manpage: update-rc.d - install and remove System-V style init script links

Provided by: init-system-helpers_1.29ubuntu4_all

NAME

       update-rc.d - install and remove System-V style init script links

SYNOPSIS

       update-rc.d [-n] [-f] name remove

       update-rc.d [-n] name defaults

       update-rc.d [-n] name disable|enable [ S|2|3|4|5 ]

DESCRIPTION

       update-rc.d  updates  the  System V style init script links /etc/rcrunlevel.d/NNname whose
       target is the script /etc/init.d/name.  These links  are  run  by  init  when  it  changes
       runlevels;  they  are  generally  used  to start and stop system services such as daemons.
       runlevel is one of the runlevels supported by init, namely, 0123456789S,  and  NN  is  the
       two-digit sequence number that determines where in the sequence init will run the scripts.

       This  manpage  documents only the usage and behaviour of update-rc.d.  For a discussion of
       the System V style init script arrangements please  see  init(8)  and  the  Debian  Policy
       Manual.

INSTALLING INIT SCRIPT LINKS

update-rc.d requires dependency and runlevel information to be provided in the init.d
script LSB comment header of all init.d scripts. See the insserv(8) manual page for
details about the LSB header format.

When run with the defaults option, update-rc.d makes links named
/etc/rcrunlevel.d/[SK]NNname that point to the script /etc/init.d/name, using runlevel and
dependency information from the init.d script LSB comment header.

If any files named /etc/rcrunlevel.d/[SK]??name already exist then update-rc.d does
nothing. The program was written this way so that it will never change an existing
configuration, which may have been customized by the system administrator. The program
will only install links if none are present, i.e., if it appears that the service has
never been installed before.

Older versions of update-rc.d also supported start and stop options. These options are no
longer supported, and are now equivalent to the defaults option.

A common system administration error is to delete the links with the thought that this
will "disable" the service, i.e., that this will prevent the service from being started.
However, if all links have been deleted then the next time the package is upgraded, the
package's postinst script will run update-rc.d again and this will reinstall links at
their factory default locations. The correct way to disable services is to configure the
service as stopped in all runlevels in which it is started by default. In the System V
init system this means renaming the service's symbolic links from S to K.

The script /etc/init.d/name must exist before update-rc.d is run to create the links.

REMOVING SCRIPTS

       When  invoked  with  the  remove  option,   update-rc.d   removes   any   links   in   the
       /etc/rcrunlevel.d  directories  to the script /etc/init.d/name.  The script must have been
       deleted already.  If the script is still present then update-rc.d  aborts  with  an  error
       message.

       update-rc.d  is  usually  called  from a package's post-removal script when that script is
       given the purge argument.  Any files in the /etc/rcrunlevel.d  directories  that  are  not
       symbolic links to the script /etc/init.d/name will be left untouched.

DISABLING INIT SCRIPT START LINKS

       When  run  with  the disable [ S|2|3|4|5 ] options, update-rc.d modifies existing runlevel
       links for the script /etc/init.d/name by  renaming  start  links  to  stop  links  with  a
       sequence number equal to the difference of 100 minus the original sequence number.

       When  run  with  the  enable [ S|2|3|4|5 ] options, update-rc.d modifies existing runlevel
       links for the script /etc/init.d/name by  renaming  stop  links  to  start  links  with  a
       sequence  number  equal  to  the positive difference of current sequence number minus 100,
       thus returning to the original sequence number that the script  had  been  installed  with
       before disabling it.

       Both of these options only operate on start runlevel links of S, 2, 3, 4 or 5. If no start
       runlevel is specified after the disable or enable keywords, the  script  will  attempt  to
       modify links in all start runlevels.

OPTIONS

       -n     Don't do anything, just show what we would do.

       -f     Force removal of symlinks even if /etc/init.d/name still exists.

EXAMPLES

       Insert links using the defaults:
          update-rc.d foobar defaults
       The equivalent dependency header would have start and stop
       dependencies on $remote_fs and $syslog, and start in
       runlevels 2-5 and stop in runlevels 0, 1 and 6.
       Remove all links for a script (assuming foobar has been deleted already):
          update-rc.d foobar remove
       Example of disabling a service:
          update-rc.d foobar disable
       Example of a command for installing a system initialization-and-shutdown script:
          update-rc.d foobar defaults
       Example of a command for disabling a system initialization-and-shutdown script:
          update-rc.d foobar disable

BUGS

       See http://bugs.debian.org/sysv-rc.

FILES

       /etc/init.d/
              The directory containing the actual init scripts.

       /etc/rc?.d/
              The directories containing the links used by init and managed by update-rc.d.

       /etc/init.d/skeleton
              Model for use by writers of init.d scripts.