VISUDO(8)						       MAINTENANCE COMMANDS							 VISUDO(8)

NAME

       visudo - edit the sudoers file

SYNOPSIS

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

DESCRIPTION

       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/vi".	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).

OPTIONS

       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 ('_') character.

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

ENVIRONMENT

       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

FILES

       /etc/sudoers	       List of who can run what

       /etc/sudoers.tmp        Lock file for visudo

DIAGNOSTICS

       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.

SEE ALSO

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

AUTHOR

       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.

CAVEATS

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

BUGS

       If you feel you have found a bug in visudo, please submit a bug report at http://www.sudo.ws/sudo/bugs/

SUPPORT

       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.

DISCLAIMER

       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)