login-utils/sulogin.8

   1 .\" Copyright (C) 1998-2006 Miquel van Smoorenburg.
   2 .\" Copyright (C) 2012 Karel Zak <kzak@redhat.com>
   3 .\"
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   5 .\" it under the terms of the GNU General Public License as published by
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  15 .\" along with this program; if not, write to the Free Software
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  18 .TH SULOGIN "8" "July 2014" "util-linux" "System Administration"
  19 .SH NAME
  20 sulogin \- single-user login
  21 .SH SYNOPSIS
  22 .BR sulogin " [options]"
  23 .RI [ tty ]
  24 .SH DESCRIPTION
  25 .B sulogin
  26 is invoked by
  27 .B init
  28 when the system goes into single-user mode.
  29 .PP
  30 The user is prompted:
  31 .IP "" .5i
  32 Give root password for system maintenance
  33 .br
  34 (or type Control\-D for normal startup):
  35 .PP
  36 If the root account is locked and --force is specified, no password is required.
  37 .PP
  38 .B sulogin
  39 will be connected to the current terminal, or to the optional \fItty\fR device that
  40 can be specified on the command line (typically
  41 .IR /dev/console ).
  42 .PP
  43 When the user exits from the single-user shell, or presses control\-D at the
  44 prompt, the system will continue to boot.
  45 .SH OPTIONS
  46 .IP "\fB\-e\fR, \fB\-\-force\fP"
  47 If the default method of obtaining the root password from the system via
  48 .BR getpwnam (3)
  49 fails, then examine
  50 .I /etc/passwd
  51 and
  52 .I /etc/shadow
  53 to get the password.  If these files are damaged or nonexistent, or when
  54 root account is locked by '!' or '*' at the begin of the password then
  55 .B sulogin
  56 will \fBstart a root shell without asking for a password\fP.
  57 .PP
  58 .IP
  59 Only use the
  60 .B \-e
  61 option if you are sure the console is physically protected against
  62 unauthorized access.
  63 .IP "\fB\-p\fR, \fB\-\-login\-shell\fP"
  64 Specifying this option causes
  65 .B sulogin
  66 to start the shell process as a login shell.
  67 .IP "\fB\-t\fR, \fB\-\-timeout \fIseconds\fP"
  68 Specify the maximum amount of time to wait for user input.  By default,
  69 .B sulogin
  70 will wait forever.
  71 .IP "\fB\-h\fR, \fB\-\-help\fP"
  72 Display help text and exit.
  73 .IP "\fB\-V\fR, \fB\-\-version\fP"
  74 Display version information and exit.
  75 .SH ENVIRONMENT VARIABLES
  76 .B sulogin
  77 looks for the environment variable
  78 .B SUSHELL
  79 or
  80 .B sushell
  81 to determine what shell to start.  If the environment variable is not set, it
  82 will try to execute root's shell from
  83 .IR /etc/passwd .
  84 If that fails, it
  85 will fall back to
  86 .IR /bin/sh .
  87 .SH AUTHOR
  88 .B sulogin
  89 was written by Miquel van Smoorenburg for sysvinit and later ported
  90 to util-linux by Dave Reisner and Karel Zak.
  91 .SH AVAILABILITY
  92 The sulogin command is part of the util-linux package and is available from
  93 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
  94 Linux Kernel Archive
  95 .UE .