visudo

     visudo [-chqsV] [-f sudoers] [-x file]

DESCRIPTION
     visudo edits the sudoers file in a safe fashion, analogous to vipw(8).
     visudo locks the sudoers file against multiple simultaneous edits, pro-
     vides 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/local/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).

     The options are as follows:

     -c, --check
                 Enable check-only mode.  The existing sudoers file will be
                 checked for syntax errors, owner and mode.  A message will be
                 printed to the standard output describing the status of
                 sudoers unless the -q option was specified.  If the check
                 completes successfully, visudo will exit with a value of 0.
                 If an error is encountered, visudo will exit with a value of
                 1.

     -f sudoers, --file=sudoers
                 Specify an 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.  In check-only mode only, the argument to -f may be '-',
                 indicating that sudoers will be read from the standard input.

     -h, --help  Display a short help message to the standard output and exit.

     -q, --quiet
     -V, --version
                 Print the visudo and sudoers grammar versions and exit.

     -x file, --export=file
                 Export sudoers in JSON format and write it to file.  If file
                 is '-', the exported sudoers policy will to be written to the
                 standard output.  The exported format is intended to be eas-
                 ier for third-party applications to parse that the tradi-
                 tional sudoers format.  The various values have explicit
                 types which removes much of the ambiguity of the sudoers for-
                 mat.

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

     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 user ID 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 undeclared
           {User,Runas,Host,Cmnd}_Alias or you have a user or host name listed
           that consists solely of uppercase letters, digits, and the under-
           score ('_') 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.

     Warning: cycle in {User,Runas,Host,Cmnd}_Alias
           The specified {User,Runas,Host,Cmnd}_Alias includes a reference to
           itself, either directly or through an alias it includes.  This is
           only a warning by default as sudo will ignore cycles when parsing
           the sudoers file.


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.

Sudo 1.8.9p5                   December 16, 2013                  Sudo 1.8.9p5
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