1SULOGIN(8)            Linux System Administrator's Manual           SULOGIN(8)
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NAME

6       sulogin - Single-user login
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SYNOPSIS

9       sulogin [ -e ] [ -p ] [ -t SECONDS ] [ TTY ]
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DESCRIPTION

12       sulogin can be invoked by init(8) when the system goes into single user
13       mode.  (This is done through an entry in inittab(5).)  Init also  tries
14       to  execute  sulogin when the boot loader (e.g., grub(8)) passes it the
15       -b option.
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17       The user is prompted
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19            Give root password for system maintenance
20            (or type Control-D for normal startup):
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22       sulogin will be connected to the current terminal, or to  the  optional
23       device  that  can be specified on the command line (typically /dev/con‐
24       sole).
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26       If the -t option is used then the program only waits the  given  number
27       of seconds for user input.
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29       If  the  -p option is used then the single-user shell is invoked with a
30       dash as the first character in argv[0].  This causes the shell  process
31       to behave as a login shell.  The default is not to do this, so that the
32       shell will not read /etc/profile or $HOME/.profile at startup.
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34       After the user exits the single-user shell, or presses control-D at the
35       prompt, the system will (continue to) boot to the default runlevel.
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ENVIRONMENT VARIABLES

38       sulogin looks for the environment variable SUSHELL or sushell to deter‐
39       mine what shell to start. If the environment variable is  not  set,  it
40       will  try  to  execute  root's shell from /etc/passwd. If that fails it
41       will fall back to /bin/sh.
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43       This is very valuable together with the -b option to init. To boot  the
44       system  into  single  user  mode,  with  the  root  file system mounted
45       read/write, using a special "fail safe" shell that is statically linked
46       (this example is valid for the LILO bootprompt)
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48       boot: linux -b rw sushell=/sbin/sash
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FALLBACK METHODS

51       sulogin  checks  the root password using the standard method (getpwnam)
52       first.  Then, if the -e option was specified,  sulogin  examines  these
53       files directly to find the root password:
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55       /etc/passwd,
56       /etc/shadow (if present)
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58       If  they  are  damaged  or nonexistent, sulogin will start a root shell
59       without asking for a password. Only use the -e option if you  are  sure
60       the console is physically protected against unauthorized access.
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AUTHOR

63       Miquel van Smoorenburg <miquels@cistron.nl>
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SEE ALSO

66       init(8), inittab(5).
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70                                  17 Jan 2006                       SULOGIN(8)
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