sulogin



SULOGIN(8)            Linux System Administrator’s Manual           SULOGIN(8)




NAME

       sulogin -- Single-user login


SYNOPSIS

       sulogin [ -e ] [ -p ] [ -t timeout ] [ tty-device ]


DESCRIPTION

       sulogin can be invoked by init(8) when the system goes into single user
       mode (this is done through an entry in inittab(5)). Init also tries  to
       execute sulogin when it is passed the -b flag from the bootmonitor (eg,
       LILO).

       The user is prompted

            Give root password for system maintenance
            (or type Control-D for normal startup):

       sulogin will connected to the current  terminal,  or  to  the  optional
       device  that  can be specified on the command line (typically /dev/con-
       sole).

       If the -p flag was set, the single-user shell will be  invoked  with  a
       dash  as the first character in argv[0]. That will cause most shells to
       behave as a login shell. The default is not to do  this,  so  that  the
       shell will not read /etc/profile or $HOME/.profile at startup.

       After the user exits the single-user shell, or presses control-d at the
       prompt, the system will (continue to) boot to the default runlevel.


ENVIRONMENT VARIABLES

       sulogin looks for the environment variable SUSHELL or sushell to deter-
       mine  what  shell  to start. If the environment variable is not set, it
       will try to execute root’s shell from /etc/passwd.  If  that  fails  it
       will fall back to /bin/sh.

       This  is  very  valuable together with the -b flag to init. To boot the
       system into single  user  mode,  with  the  root  file  system  mounted
       read/write,  using a special "failsafe" shell that is statically linked
       (this example is valid for the LILO bootprompt)

       boot: linux -b rw sushell=/sbin/sash


FALLBACK METHODS

       sulogin checks the root password using the standard methods first.   If
       the  -e  option  was specified, sulogin examines the next files to find
       the root password. If they are damaged, or non-existant,  it  will  use
       fallback  methods  that  even  go so far as to provide you with a shell
       prompt without asking for the root password if  they  are  irrepairably
       damaged.

       /etc/passwd,
       /etc/shadow (if present)


AUTHOR

       Miquel van Smoorenburg <miquels@cistron.nl>


SEE ALSO

       init(8), inittab(5).



                                  11 Sep 2000                       SULOGIN(8)

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