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Linux 2.6 - man page for visudo (linux section 8)


       visudo - edit the sudoers file

       visudo [-c] [-q] [-s] [-V] [-f sudoers]

       visudo edits the sudoers file in a safe fashion, analogous to vipw(8).  visudo locks the
       sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks
       for parse errors.  If the sudoers file is currently being edited you will receive a
       message to try again later.

       There is a hard-coded list of one or more editors that visudo will use set at compile-time
       that may be overridden via the editor sudoers Default variable.	This list defaults to
       "/usr/bin/editor".  Normally, visudo does not honor the VISUAL or EDITOR environment
       variables unless they contain an editor in the aforementioned editors list.  However, if
       visudo is configured with the --with-env-editor option or the env_editor Default variable
       is set in sudoers, visudo will use any the editor defines by VISUAL or EDITOR.  Note that
       this can be a security hole since it allows the user to execute any program they wish
       simply by setting VISUAL or EDITOR.

       visudo parses the sudoers file after the edit and will not save the changes if there is a
       syntax error.  Upon finding an error, visudo will print a message stating the line
       number(s) where the error occurred and the user will receive the "What now?" prompt.  At
       this point the user may enter "e" to re-edit the sudoers file, "x" to exit without saving
       the changes, or "Q" to quit and save changes.  The "Q" option should be used with extreme
       care because if visudo believes there to be a parse error, so will sudo and no one will be
       able to sudo again until the error is fixed.  If "e" is typed to edit the  sudoers file
       after a parse error has been detected, the cursor will be placed on the line where the
       error occurred (if the editor supports this feature).

       visudo accepts the following command line options:

       -c	   Enable check-only mode.  The existing sudoers file will be checked for syntax
		   and a message will be printed to the standard output detailing the status of
		   sudoers.  If the syntax check completes successfully, visudo will exit with a
		   value of 0.	If a syntax error is encountered, visudo will exit with a value
		   of 1.

       -f sudoers  Specify and alternate sudoers file location.  With this option visudo will
		   edit (or check) the sudoers file of your choice, instead of the default,
		   /etc/sudoers.  The lock file used is the specified sudoers file with ".tmp"
		   appended to it.

       -q	   Enable quiet mode.  In this mode details about syntax errors are not printed.
		   This option is only useful when combined with the -c option.

       -s	   Enable strict checking of the sudoers file.	If an alias is used before it is
		   defined, visudo will consider this a parse error.  Note that it is not
		   possible to differentiate between an alias and a host name or user name that
		   consists solely of uppercase letters, digits, and the underscore ('_')

       -V	   The -V (version) option causes visudo to print its version number and exit.

       The following environment variables may be consulted depending on the value of the editor
       and env_editor sudoers variables:

       VISUAL	       Invoked by visudo as the editor to use

       EDITOR	       Used by visudo if VISUAL is not set

       /etc/sudoers	       List of who can run what

       /etc/sudoers.tmp        Lock file for visudo

       sudoers file busy, try again later.
	   Someone else is currently editing the sudoers file.

       /etc/sudoers.tmp: Permission denied
	   You didn't run visudo as root.

       Can't find you in the passwd database
	   Your userid does not appear in the system passwd file.

       Warning: {User,Runas,Host,Cmnd}_Alias referenced but not defined
	   Either you are trying to use an undeclare {User,Runas,Host,Cmnd}_Alias or you have a
	   user or host name listed that consists solely of uppercase letters, digits, and the
	   underscore ('_') character.	In the latter case, you can ignore the warnings (sudo
	   will not complain).	In -s (strict) mode these are errors, not warnings.

       Warning: unused {User,Runas,Host,Cmnd}_Alias
	   The specified {User,Runas,Host,Cmnd}_Alias was defined but never used.  You may wish
	   to comment out or remove the unused alias.  In -s (strict) mode this is an error, not
	   a warning.

       vi(1), sudoers(5), sudo(8), vipw(8)

       Many people have worked on sudo over the years; this version of visudo was written by:

	Todd Miller

       See the HISTORY file in the sudo distribution or visit
       http://www.sudo.ws/sudo/history.html for more details.

       There is no easy way to prevent a user from gaining a root shell if the editor used by
       visudo allows shell escapes.

       If you feel you have found a bug in visudo, please submit a bug report at

       Limited free support is available via the sudo-users mailing list, see
       http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.

       visudo is provided ``AS IS'' and any express or implied warranties, including, but not
       limited to, the implied warranties of merchantability and fitness for a particular purpose
       are disclaimed.	See the LICENSE file distributed with sudo or
       http://www.sudo.ws/sudo/license.html for complete details.

1.7.4					  July 14, 2010 				VISUDO(8)

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