# 2.11BSD#431 - /usr/man/cat8/init.0

    INIT(8)             UNIX Programmer's Manual		  INIT(8)

    NAME
         init - process control initialization

    SYNOPSIS
         /etc/init

    DESCRIPTION
         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 com-
         mences 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 hit-
         ting ^D), init runs /etc/rc without the reboot parameter.
         This command file performs housekeeping operations such as
         removing temporary files, mounting file systems, and start-
         ing 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 executes a
         command for each terminal specified in the file.  This com-
         mand 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 appropri-
         ate terminal is reopened and getty is reinvoked.

         Init catches the hangup signal (signal SIGHUP) and inter-
         prets 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 pro-
         cess: 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

    Printed 11/24/99	November 27, 1996			1

    INIT(8)             UNIX Programmer's Manual		  INIT(8)

         are deadlocked (due to hardware or software failure), init
         will not wait for them all to die (which might take for-
         ever), but will time out after 30 seconds and print a warn-
         ing message.

         Init will cease creating new getty's and allow the system to
         slowly die away, if it is sent a terminal stop (TSTP) sig-
         nal, 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.

    DIAGNOSTICS
         /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,

         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.

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

    SEE ALSO
         login(1), kill(1), sh(1), ttys(5), crash(8), getty(8),
         rc(8), reboot(8), halt(8), shutdown(8)

    Printed 11/24/99	November 27, 1996			2

Generated: 2016-12-26 | Generated by man2html V0.25 page hit count: 740 |