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Unix Version 7 - man page for init (v7 section 8)

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INIT(8) 										  INIT(8)

       init, rc  -  process control initialization


       Init  is invoked as the last step of the boot procedure (see boot(8)).  Generally its role
       is to create a process for each typewriter on which a user may log in.

       When init first is executed the console typewriter /dev/console.  is  opened  for  reading
       and writing and the shell is invoked immediately.  This feature is used to bring up a sin-
       gle-user system.  If the shell terminates,  init  comes	up  multi-user	and  the  process
       described below is started.

       When  init comes up multiuser, it invokes a shell, with input taken from the file /etc/rc.
       This command file performs housekeeping like removing temporary files, mounting file  sys-
       tems, and starting daemons.

       Then  init  reads  the file /etc/ttys and forks several times to create a process for each
       typewriter specified in the file.  Each of these processes  opens  the  appropriate  type-
       writer  for reading and writing.  These channels thus receive file descriptors 0, 1 and 2,
       the standard input, output and error files.  Opening the typewriter will usually involve a
       delay,  since the open is not completed until someone is dialed up and carrier established
       on the channel.	Then /etc/getty is called with argument as specified by the last  charac-
       ter of the ttys file line.  Getty reads the user's name and invokes login(1) 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 /usr/adm/wtmp, which maintains a history of
       logins and logouts.  Then the appropriate typewriter is reopened and getty is reinvoked.

       Init catches the hangup signal SIGHUP and interprets it to mean that the system should  be
       brought from multi user to single user.	Use `kill -1 1' to send the hangup signal.

       /dev/tty?, /etc/utmp, /usr/adm/wtmp, /etc/ttys, /etc/rc

       login(1), kill(1), sh(1), ttys(5), getty(8)

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