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BSD 2.11 - man page for init (bsd section 8)

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INIT(8) 										  INIT(8)

       init - process control initialization


       Init is invoked inside UNIX as the last step in the boot procedure.  It normally then runs
       the automatic reboot sequence as described in reboot(8),  and  if  this	succeeds,  begins
       multi-user  operation.	If the reboot fails, it commences single user operation by giving
       the super-user a shell on the console.  It is possible to pass parameters  from	the  boot
       program	to init so that single user operation is commenced immediately.  When such single
       user operation is terminated by killing the single-user shell (i.e. by hitting  ^D),  init
       runs /etc/rc without the reboot parameter.  This command file performs housekeeping opera-
       tions such as removing temporary files, mounting file systems, and starting daemons.

       In multi-user operation, init's role is to create a process  for  each  terminal  port  on
       which  a  user may log in.  To begin such operations, it reads the file /etc/ttys and exe-
       cutes a command for each terminal specified in the file.  This  command	will  usually  be
       /usr/libexec/getty.   Getty opens and initializes the terminal line, reads the user's name
       and invokes login to log in the user and execute the Shell.

       Ultimately the Shell will terminate because of an end-of-file either typed  explicitly  or
       generated  as  a  result of hanging up.	The main path of init, which has been waiting for
       such an event, wakes up and removes the	appropriate  entry  from  the  file  utmp,  which
       records	current  users, and makes an entry in the wtmp, file which maintains a history of
       logins and logouts.  The wtmp entry is made only if a user logged in successfully  on  the
       line.  Then the appropriate terminal is reopened and getty is reinvoked.

       Init  catches  the  hangup  signal (signal SIGHUP) and interprets it to mean that the file
       /etc/ttys should be read again.	The Shell process on each line which used to be active in
       ttys  but  is no longer there is terminated; a new process is created for each added line;
       lines unchanged in the file are undisturbed.  Thus it is possible to drop or add  terminal
       lines  without  rebooting the system by changing the ttys file and sending a hangup signal
       to the init process: use `kill -HUP 1.'

       Init will terminate multi-user operations and resume single-user mode if sent a	terminate
       (TERM)  signal, i.e. ``kill -TERM 1''.  If there are processes outstanding which are dead-
       locked (due to hardware or software failure), init will not  wait  for  them  all  to  die
       (which  might  take  forever), but will time out after 30 seconds and print a warning mes-

       Init will cease creating new getty's and allow the system to slowly die	away,  if  it  is
       sent  a	terminal  stop	(TSTP) signal, i.e. ``kill -TSTP 1''.  A later hangup will resume
       full multi-user operations, or a terminate will initiate a single user shell.   This  hook
       is used by reboot(8) and halt(8).

       Init's  role  is so critical that if it dies, the system will reboot itself automatically.
       If, at bootstrap time, the init process cannot be located, the system will  loop  in  user
       mode at location 0x13.

       /usr/libexec/getty gettyargs failing, sleeping.	A process being started to service a line
       is exiting quickly each time it is started.  This is often caused by a  ringing	or  noisy
       terminal line.  Init will sleep for 30 seconds, then continue trying to start the process.

       WARNING: Something is hung (wont die); ps axl advised.  A process is hung and could not be
       killed when the system was shutting down.  This is usually caused by a  process	which  is
       stuck in a device driver due to a persistent device error condition.

       /dev/console, /dev/tty*, /var/run/utmp, /usr/adm/wtmp, /etc/ttys, /etc/rc

       login(1),  kill(1),  sh(1),  ttys(5), crash(8), getty(8), rc(8), reboot(8), halt(8), shut-

4th Berkeley Distribution		November 27, 1996				  INIT(8)
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