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init(8) [v7 man page]

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

NAME
init, rc - process control initialization SYNOPSIS
/etc/init /etc/rc DESCRIPTION
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 single-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 systems, 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 typewriter 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 character 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 cur- rent 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. FILES
/dev/tty?, /etc/utmp, /usr/adm/wtmp, /etc/ttys, /etc/rc SEE ALSO
login(1), kill(1), sh(1), ttys(5), getty(8) INIT(8)

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

NAME
init - grandparent of all processes DESCRIPTION
The first program started by Minix is init. The actions performed by init can be summarized by this pseudo shell program: # Open 0, 1, 2. exec </dev/null >/dev/log 2>&1 # Run the system initialization script. sh /etc/rc $bootopts >/etc/utmp echo reboot >>/usr/adm/wtmp while :; do # Wait for a process to exit, but don't always block. wait # Record logout. (Not in this dumb way, of course.) if "pid is in my tables" $pid then echo "logout $pid" >/etc/utmp echo "logout $pid" >>/usr/adm/wtmp fi # Start a new session. while read line type getty init do if idle $line then $init ... <$tty >$tty $getty <$tty >$tty 2>&1 & pid=$! "add pid to tables" $pid echo "login $line $pid" >/etc/utmp echo "login $line $pid" >>/usr/adm/wtmp fi done < /dev/ttytab done The first action of init is to run /etc/rc to initialize the system as described in boot(8). Init then enters its main loop where it waits for processes to exit, and starts processes on each enabled terminal line. The file /etc/ttytab contains a list of terminal devices, their terminal types, the program to execute on them to allow one to login (usually getty(8)), and the program to execute first to initialize the line (usually stty(1)). These fields may be left out to indicate that a line is disabled or that initialization is not necessary. The commands are searched using the path /sbin:/bin:/usr/sbin:/usr/bin. Init accepts several signals that must be sent to process id 1. (It is the first process, so natually its process id is 1.) The signals are: SIGHUP When receiving a hangup signal, init will forget about errors and rescan ttytab for processes to execute. Init normally rescans ttytab each time it feels the need to respawn a process, so the hangup signal is only needed if a line has been shut down, or after a terminate signal. Note that after turning a line off you will have to kill the process running on that line manually, init doesn't do that for you. SIGTERM Normally sent by programs that halt or reboot Minix. Causes init to stop spawning new processes. SIGABRT Sent by the keyboard driver when the CTRL-ALT-DEL key combination is typed. Causes init to run the shutdown command. A second abort signal makes init halt the system directly with a system call. The keyboard driver halts the system, without a sync, after the third CTRL-ALT-DEL. Minix vs. Minix-vmd There are a few differences between standard Minix and Minix-vmd on how init is run. The /etc/rc file is executed under standard Minix with input connected to /dev/console, but under Minix-vmd this is still /dev/null. This means that under Minix-vmd processes must be reconnected to /dev/console with the intr program if they need user interaction. Minix-vmd passes the value of the bootopts boot variable to /etc/rc. Standard Minix does not. FILES
/etc/ttytab List of terminals devices. /etc/utmp List of currently logged in users. /usr/adm/wtmp Login/logout history. SEE ALSO
ttytab(5), utmp(5), getty(8), stty(1), boot(8). AUTHOR
Kees J. Bot (kjb@cs.vu.nl) INIT(8)
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