MirOS Manual: init(8)

INIT(8)                  BSD System Manager's Manual                   INIT(8)

NAME

     init - process control initialisation

SYNOPSIS

     init [-fs]

DESCRIPTION

     The init program is the last stage of the boot process. It normally runs
     the automatic reboot sequence as described in reboot(8), and if this
     succeeds, begins multi-user operation. If the reboot scripts fail, init
     commences single-user operation by giving the superuser a shell on the
     console. The init program may be passed parameters from the boot program
     to prevent the system from going multi-user and to instead execute a
     single-user shell without starting the normal daemons.

     The following parameters may be passed from the boot program:

     -f      Activate fastboot mode.

     -s      Boot directly into single user mode.

     The system is then quiescent for maintenance work and may later be made
     to go to multi-user by exiting the single-user shell (with ^D). This
     causes init to run the /etc/rc startup command file in fastboot mode
     (skipping disk checks).

     If the console entry in the ttys(5) file does not contain the "secure"
     flag, then init will require that the superuser password be entered be-
     fore the system will start a single-user shell. The password check is
     skipped if the console is marked as "secure".

     The kernel securelevel(7) is normally set to 0 while in single-user mode,
     and raised to 1 when the system begins multi-user operations. This action
     will not take place if the securelevel is -1, and can be modified via the
     /etc/rc.securelevel script.

     In multi-user operation, init maintains processes for the terminal ports
     found in the file ttys(5). init reads this file, and executes the command
     found in the second field. This command is usually getty(8); getty opens
     and initialises the tty line and executes the login program. The login
     program, when a valid user logs in, executes a shell for that user. When
     this shell dies, either because the user logged out or an abnormal termi-
     nation occurred (a signal), the init program wakes up, deletes the user
     from the utmp(5) file of current users and records the logout in the wtmp
     file. The cycle is then restarted by init executing a new getty for the
     line.

     Line status (on, off, secure, getty, or window information) may be
     changed in the ttys file without a reboot by sending the signal SIGHUP to
     init with the command "kill -HUP 1". On receipt of this signal, init re-
     reads the ttys file. When a line is turned off in ttys, init will send a
     SIGHUP signal to the controlling process for the session associated with
     the line. For any lines that were previously turned off in the ttys file
     and are now on, init executes a new getty to enable a new login. If the
     getty or window field for a line is changed, the change takes effect at
     the end of the current login session (e.g., the next time init starts a
     process on the line). If a line is commented out or deleted from ttys,
     init will not do anything at all to that line. However, it will complain
     that the relationship between lines in the ttys file and records in the
     utmp file is out of sync, so this practice is not recommended.

     init will terminate multi-user operations and resume single-user mode if
     sent a terminate (TERM) signal, for example, "kill -TERM 1". If there are
     processes outstanding that are deadlocked (because of 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 gettys 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 start a single-user shell. This hook is used by reboot(8) and
     halt(8).

     init will terminate multi-user operations, kill all gettys, run /etc/rc
     shutdown, and halt the machine if user-defined signal 1 (USR1) is re-
     ceived, e.g. by "kill -USR1 1".

     The role of init 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 panic with the message "panic: init died (signal
     %d, exit %d)".

RESOURCES

     When init spawns a process it sets the process priority, umask, and
     resource limits based on /etc/login.conf. When starting the rc(8) files,
     the login class "daemon" is used. When starting a window system or
     getty(8), the login class "default" is used. No resource changes are made
     when entering single user mode.

FILES

     /dev/console         system console device
     /dev/tty*            terminal ports found in ttys
     /var/run/utmp        record of users currently logged in
     /var/log/wtmp        record of all logins and logouts
     /etc/ttys            terminal initialisation information file
     /etc/rc              system startup commands
     /etc/rc.securelevel  commands that run before the security level changes
     /etc/rc.shutdown     script run at shutdown time via /etc/rc
     /var/db/host.random  where 2 KiB entropy are stored on SIGUSR1

DIAGNOSTICS

     getty repeating too quickly on port %s, 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 10
     seconds, then continue trying to start the process.

     some processes would not die; ps axl advised.  A process is hung and
     could not be killed when the system was shutting down. This condition is
     usually caused by a process that is stuck in a device driver because of a
     persistent device error condition.

SEE ALSO

     kill(1), login(1), sh(1), fbtab(5), login.conf(5), ttys(5),
     securelevel(7), crash(8), getty(8), halt(8), rc(8), rc.shutdown(8),
     reboot(8), shutdown(8)

HISTORY

     An init command appeared in Version 6 AT&T UNIX.

MirOS BSD #10-current         February 19, 2011                              1

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