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 "/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)