init man page on DigitalUNIX

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init(8)								       init(8)

       init - Process control initialization

       /sbin/init  [0123456789MmQqSs]

       Shuts  down and halts the system.  Changes the run level to a multiuser
       state with local processes and daemons.	Changes the  run  level	 to  a
       multiuser  state	 with remote processes and daemons.  Changes run level
       to that specified by the number option in the /etc/inittab file.	 If no
       such  entry exists, no action is taken and no message is output.	 Moves
       control to the console device and halts to  single-user	mode.	Forces
       init  to	 reexamine  the entries in the inittab file and terminates any
       live processes which have had their configuration entries removed  from
       /etc/inittab.  Users should be aware that when a getty(8) line has been
       removed from/etc/inittab, and a login shell is active on	 the  terminal
       line  that  was	formerly  designated  in inittab as a getty entry, the
       login shell will be killed.  Changes the run level  to  a  single  user
       state with only the essential kernel services.

       The  init  program  initializes	the system by creating and controlling
       processes. The processes run by init at each run level are  defined  in
       the  inittab  file. The init program reads and processes the entries in
       the inittab file.

       The init program considers the system to be in a run level at any given
       time; each run level has a specific group of processes that run at that
       level. The init program operates in one of eleven run levels:  0-9  and
       Ss.  Of	these,	only  -0, -s, -2, and -3 are configured in the inittab
       file by default.

       The run level changes when a privileged user invokes init. The new init
       sends  appropriate  signals to the original init that tell it which run
       level to change to.

       Running the init program is the last step in the boot process after the
       root  file  system is mounted.  The init program scans the inittab file
       and looks for an entry with the initdefault keyword.  If the  entry  is
       there,  init  uses the run level specified in that entry as the initial
       run level to enter. If the entry is not found  in  the<filename>	 init‐
       tab</filename>  file  or	 if  the  inittab  file	 does  not exist, init
       requests that the user enter a  run  level  from	 the  system  console,
       /dev/console.  If the user enters the letter s, init enters single user
       state, assigns the virtual console terminal to the user's terminal  and
       opens  it  for  reading and writing.  The su command is invoked and the
       system displays a message on the console stating the  location  of  the
       virtual console.

       To  change  the	run level, the user specifies either the 0, 2, 3, or s

       For the first post-boot execution of init to a  run  level  other  than
       single  user,   it searches the inittab file for entries at the new run
       level that have the boot or bootwait keywords.  If the run  level  that
       is  specified matches the entry, the init program acts on these entries
       before processing other entries in the inittab file.  Any special  ini‐
       tialization  of the system, such as checking and mounting file systems,
       takes place before users are allowed on the system.  The	 init  program
       then  scans the inittab file to find all entries that are to be handled
       for that level.

       Before starting a new process, init reads each  entry  in  the  inittab
       file,  and  for each entry that should be respawned, init forks a child
       process.	 After spawning all required processes, init waits for one  of
       its descendant processes to stop, a power-fail signal, or a signal that
       it should change the run level. If one of the  preceding	 three	condi‐
       tions occurs, init reexamines the inittab file. You can add new entries
       to the inittab file, but init does not reexamine the file until one  of
       the three previous conditions actually occurs. To immediately reexamine
       the inittab file, invoke the init program with the q option.

       Specifies the command path Specifies  the  init	command	 control  file
       Specifies the permanent login accounting file

       Commands: getty(8), rc0(8), rc2(8), rc3(8), shutdown(8)

       Functions: kill(2), reboot(2)

       Files: inittab(4)


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