INIT(8)                 COMMAND REFERENCE                 INIT(8)



NAME
     init - process control initialization

SYNOPSIS
     /etc/init

DESCRIPTION
     Init is invoked inside UTek as the last step in the boot
     procedure.  It normally runs the automatic startup sequence,
     which is determined by the shell script /etc/rc. This
     command file performs housekeeping operations such as
     removing temporary files, mounting file systems, and
     starting daemons.  If it succeeds, init begins multi-user
     operation, which is the normal operating mode of UTek, even
     for a single user workstation. The terms multi-user and
     single-user are unfortunate artifacts of UTek's heritage as
     a timesharing operating system.

     For multi-user operation, init creates a process for each
     terminal or display port on which a user may log in.  It
     forks as needed to create a process for each port specified
     in the file /etc/ttys.  Each of these processes opens the
     appropriate port for reading and writing.  Opening a port
     may involve a delay on terminal ports, since the open may
     not complete until the terminal is fully connected and
     ready.  If a terminal exists but an error occurs when trying
     to open the terminal, init complains by writing a message to
     the system console; the message is repeated every 10 minutes
     for each such terminal until the terminal is shut off in
     /etc/ttys and init is notified (by a hangup signal, as
     described here), or the terminal becomes accessible (init
     checks again every minute).

     After an open succeeds, /etc/getty is called with the
     argument specified by the second character of the ttys file
     line.  The command getty reads the user's name and invokes
     the login command to log in the user and execute the
     appropriate shell.

     Ultimately the Shell terminates because an end-of-file was
     either typed explicitly or was 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.  The wtmp entry is made only if a
     user logged in successfully.  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.  For ports which were active but are no longer



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INIT(8)                 COMMAND REFERENCE                 INIT(8)



     active, the controlling process (shell or getty) is
     terminated.  For newly active ports getty is started.  Ports
     unchanged in the file are undisturbed.  Thus it is possible
     to drop or add phone lines without rebooting the system by
     changing the ttys file and sending a hangup signal to the
     init process; use:

          kill -HUP 1

     Init terminates multi-user operations and resumes single-
     user mode if sent a terminate (TERM) signal (i.e.,   kill
     -TERM 1).  If there are processes outstanding which are
     deadlocked (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 message.

     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).

     Single-user mode provides the console with a shell, with no
     other user-level processes running.  This allows controlled
     operation of the system such that no background cpu or disk
     activity can occur.  It is required for some maintenance
     activities, such as checking active file systems.

     Single-user mode can be entered by several means.  Some
     failures of automatic startup will drop the console into
     single-user mode.  It can be entered intentionally from the
     boot process or by using the shutdown command with no
     options in multi-user mode.  When single user operation is
     terminated by killing the single-user shell (i.e., by typing
     control-D), init runs commences automatic startup.

     Since all single-user operations are performed as superuser,
     running in single-user mode is protected by the root passwd,
     regardless of how it is entered.  When the single-user shell
     is terminated (i.e., by typing control-D), confirmation is
     requested so that unwanted multi-user activity won't be
     started inadvertently.

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




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DIAGNOSTICS
     init: tty: cannot open.
          A terminal which is turned on in the ttys file cannot
          be opened, usually because the requisite lines are
          either not configured into the system or the associated
          device was not attached during boot-time system
          configuration.

     WARNING: Something is hung (won't 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.

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






































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