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Annotation of researchv10dc/man/man8/init.8, revision 1.1.1.1

1.1       root        1: .TH INIT 8
                      2: .CT 1 sa_auto secur
                      3: .SH NAME
                      4: init \- process control initialization
                      5: .SH SYNOPSIS
                      6: .B /etc/init
                      7: .SH DESCRIPTION
                      8: .I Init
                      9: is invoked by the operating system as the last step in the boot procedure.
                     10: It is always process 1.
                     11: .PP
                     12: When started normally,
                     13: .I init
                     14: calls
                     15: .IR rc (8)
                     16: with parameter
                     17: .BR autoboot .
                     18: If this succeeds,
                     19: .I init
                     20: begins multi-user operation.
                     21: If
                     22: .I rc
                     23: fails,
                     24: .I init
                     25: commences single user operation by giving
                     26: the super-user a shell on the console.
                     27: It is possible to pass parameters
                     28: from the boot program to
                     29: .I init
                     30: so that single user operation is commenced immediately.
                     31: When the single user shell terminates,
                     32: .I init
                     33: runs
                     34: .IR rc
                     35: without the parameter,
                     36: and begins multi-user operation.
                     37: .PP
                     38: .I Rc
                     39: performs housekeeping
                     40: such as checking and mounting file systems
                     41: and starting daemons;
                     42: see
                     43: .IR rc (8).
                     44: .PP
                     45: In multi-user operation,
                     46: .IR init 's
                     47: role is to create a process for each
                     48: directly connected terminal port on which a user may log in.
                     49: To begin such operations, it reads the
                     50: .IR ttys (5)
                     51: file and forks to create a process
                     52: for each terminal specified in the file.
                     53: Each of these processes opens the appropriate terminal
                     54: for reading and writing
                     55: on file descriptors 0, 1, 2, and 3 (the standard input and
                     56: output, the diagnostic output and
                     57: .FR /dev/tty ).
                     58: Opening the terminal will usually involve a delay,
                     59: since the
                     60: .I open 
                     61: is not completed until someone
                     62: dials and carrier is established on the channel.
                     63: Then
                     64: .IR getty (8)
                     65: is called with argument as specified by the second character of
                     66: the
                     67: .I ttys
                     68: file line.
                     69: .I Getty
                     70: reads the user's name and invokes
                     71: .IR login (8)
                     72: to log in the user and execute the shell.
                     73: .PP
                     74: Ultimately the shell will terminate
                     75: because of an end-of-file or as a result of hanging up.
                     76: The main path of
                     77: .IR init ,
                     78: which has been waiting
                     79: for such an event,
                     80: wakes up and removes the appropriate entry from the
                     81: file
                     82: .IR utmp (5),
                     83: which records current users, and
                     84: makes an entry in
                     85: .IR wtmp ,
                     86: which maintains a history
                     87: of logins and logouts.
                     88: Then the appropriate terminal is reopened and
                     89: .I getty
                     90: is
                     91: invoked again.
                     92: .PP
                     93: .I Init
                     94: catches signal
                     95: .B SIGHUP
                     96: and interprets it to mean that
                     97: the
                     98: .I ttys
                     99: file
                    100: should be read again.
                    101: The shell process on each line that has become inactive 
                    102: according to
                    103: .I ttys
                    104: is terminated;
                    105: a new process is created for each line added;
                    106: lines unchanged in the file are undisturbed.
                    107: Thus it is possible to drop or add terminal lines without
                    108: rebooting the system by changing the
                    109: .I ttys
                    110: file and sending a
                    111: .I hangup
                    112: signal to the
                    113: .I init
                    114: process: use
                    115: .LR "kill -1 1" .
                    116: .PP
                    117: .I Init
                    118: will terminate multi-user operations,
                    119: kill all outstanding processes,
                    120: and resume single-user mode
                    121: if sent signal
                    122: .BR SIGTERM :
                    123: use
                    124: .LR "kill 1" .
                    125: .I Init
                    126: will wait at most 30 seconds for outstanding processes to die,
                    127: to avoid waiting forever.
                    128: .PP
                    129: If, at bootstrap time, the
                    130: .I init
                    131: program cannot be executed,
                    132: the system will loop in user mode at a low address.
                    133: .SH FILES
                    134: .nf
                    135: .F /dev/console
                    136: .F /dev/tty
                    137: .F /etc/utmp
                    138: .F /usr/adm/wtmp
                    139: .F /etc/ttys
                    140: .F /etc/rc
                    141: .fi
                    142: .SH "SEE ALSO"
                    143: .IR login (8), 
                    144: .IR kill (1), 
                    145: .IR sh (1), 
                    146: .IR ttys (5), 
                    147: .IR getty (8), 
                    148: .IR rc (8), 
                    149: .IR reboot (8)
                    150: .SH BUGS
                    151: .IR Init 's
                    152: multi-user functions should be integrated
                    153: with the world of
                    154: .IR svcmgr (8).

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