init



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


NAME

     init - process control initialization


SYNOPSIS

     init [-fs]


DESCRIPTION

     The init program is the last stage of the boot process.  It normally
     executes the sequence of events described in rc(8) and begins multi-user
     operation.

     The kernel may pass the following options to init, usually when requested
     by the boot(8) program:

     -f      Activate fastboot mode.  This is not currently supported by the
             OpenBSD kernel.  Instead, use the /fastboot file as explained in
             the rc(8) manual.

     -s      Boot directly into single-user mode.

     Single-user mode is also entered if the boot scripts fail.

     In single-user mode, the rc(8) script is not run and normal daemons are
     not started, but instead a super-user shell is started on the system
     console.  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 before the system will start a single-user shell.  The password
     check is skipped if the console is marked as "secure".

     In single-user mode, the system is 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 rc(8) startup command file in fastboot
     mode (skipping disk checks).

     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 initializes 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 termination 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 -s 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 -s 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 getty(8) and allow the system to slowly die
     away, if it is sent a terminal stop (TSTP) signal, i.e., "kill -s 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 getty(8), and run
     /etc/rc.shutdown if a user-defined signal 1 (USR1), user-defined signal 2
     (USR2), or interrupt (INT) signal is received.  Following this, USR1 will
     halt the system; USR2 will request a powerdown; and INT will cause a
     reboot.  /etc/rc.shutdown can specify that a powerdown is requested
     instead of the action specified by the signal.

     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
     /etc/rc              system startup commands
     /etc/rc.securelevel  commands that run before the security level changes
     /etc/rc.shutdown     script run at shutdown time
     /etc/ttys            terminal initialization information file
     /fastboot            tells rc(8) not to run fsck(8) during the next boot
     /var/run/utmp        record of users currently logged in
     /var/log/wtmp        record of all logins and logouts


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 1 AT&T UNIX.

OpenBSD 6.2                     October 6, 2016                    OpenBSD 6.2

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