login-utils/simpleinit.8

   1 .\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu)
   2 .\" May be distributed under the GNU General Public License
   3 .\" " for emacs's hilit19 mode :-)
   4 .TH SIMPLEINIT 8 "20 November 1993" "Linux 0.99" "Linux Programmer's Manual"
   5 .SH NAME
   6 simpleinit \- process control initialization
   7 .SH SYNOPSIS
   8 .B "init [ single ]"
   9 .SH DESCRIPTION
  10 .B init
  11 is invoked as the last step in the Linux boot sequence.  If the
  12 .B single
  13 option is used, or if the file
  14 .I /etc/singleboot
  15 exists, then single user mode will be entered, by starting
  16 .IR /bin/sh .
  17 If the file
  18 .I /etc/securesingle
  19 exists, then the root password will be required to start single user mode.
  20 If the root password does not exist, or if
  21 .I /etc/passwd
  22 does not exist, the checking of the password will be skipped.
  23
  24 If the file
  25 .I /etc/TZ
  26 exists, then the contents of that file will be read, and used to set the TZ
  27 environment variable for each process started by
  28 .BR simpleinit .
  29 This "feature" is only available if it's configured at compile-time. It's
  30 not normally needed.
  31
  32 After single user mode is terminated, the
  33 .I /etc/rc
  34 file is executed, and the information in
  35 .I /etc/inittab
  36 will be used to start processes.
  37
  38 While
  39 .B init
  40 is running, several signals are trapped, with special action taken.  Since
  41 .B init
  42 has PID 1, sending signals to the
  43 .B init
  44 process is easy with the
  45 .BR kill (1)
  46 command.
  47
  48 If
  49 .B init
  50 catches a SIGHUP (hangup) signal, the
  51 .I /etc/inittab
  52 will be read again.
  53
  54 If
  55 .B init
  56 catches a SIGTSTP (terminal stop) signal, no more processes will be
  57 spawned.  This is a toggle, which is reset is
  58 .B init
  59 catches another SIGTSTP signal.
  60
  61 If
  62 .B init
  63 catches a SIGINT (interrupt) signal,
  64 .B init
  65 will sync a few times, and try to start
  66 .IR reboot .
  67 Failing this,
  68 .B init
  69 will execute the system
  70 .BR reboot (2)
  71 call.  Under Linux, it is possible to configure the Ctrl-Alt-Del sequence
  72 to send a signal to
  73 .B init
  74 instead of rebooting the system.
  75 .SH "THE INITTAB FILE"
  76 Because of the number of init programs which are appearing in the Linux
  77 community, the documentation for the
  78 .I /etc/inittab
  79 file, which is usually found with the
  80 .BR inittab (5)
  81 man page, is presented here:
  82
  83 The format is
  84
  85 .RS
  86 .B "ttyline:termcap-entry:getty-command"
  87 .RE
  88
  89 An example is as follows:
  90
  91 .nf
  92 .RS
  93 tty1:linux:/sbin/getty 9600 tty1
  94 tty2:linux:/sbin/getty 9600 tty2
  95 tty3:linux:/sbin/getty 9600 tty3
  96 tty4:linux:/sbin/getty 9600 tty4
  97 # tty5:linux:/sbin/getty 9600 tty5
  98 # ttyS1:dumb:/sbin/getty 9600 ttyS1
  99 # ttyS2:dumb:/sbin/getty -m -t60 2400 ttyS2
 100 .RE
 101 .fi
 102
 103 Lines beginning with the
 104 .B #
 105 character are treated as comments.  Please see documentation for the
 106 .B getty (8)
 107 command that you are using, since there are several of these in the Linux
 108 community at this time.
 109 .SH FILES
 110 .I /etc/inittab
 111 .br
 112 .I /etc/singleboot
 113 .br
 114 .I /etc/securesingle
 115 .br
 116 .I /etc/TZ
 117 .br
 118 .I /etc/passwd
 119 .br
 120 .I /etc/rc
 121 .SH "SEE ALSO"
 122 .BR inittab (5),
 123 .BR ctrlaltdel (8)
 124 .BR reboot (8),
 125 .BR termcap (5),
 126 .BR getty (8),
 127 .BR agetty (8),
 128 .BR shutdown (8)
 129 .SH BUGS
 130 This program is called
 131 .B simpleinit
 132 to distinguish it from the System V compatible versions of init which are
 133 starting to appear in the Linux community.
 134 .B simpleinit
 135 should be linked to, or made identical with,
 136 .I init
 137 for correct functionality.
 138 .SH AUTHOR
 139 Peter Orbaek (poe@daimi.aau.dk)
 140 .br
 141 Version 1.20, with patches for singleuser mode by Werner Almesberger
 142