VISUDO(1m)                   MAINTENANCE COMMANDS                   VISUDO(1m)



NAME
       visudo - edit the sudoers file

SYNOPSIS
       visudo [-chqsV] [-f sudoers]

DESCRIPTION
       visudo edits the sudoers file in a safe fashion, analogous to vipw(1m).
       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 "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 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  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.  In check-only mode only, the argument to
                   -f may be "-", indicating that sudoers will be read from
                   the standard input.

       -h          The -h (help) option causes visudo to print a short help
                   message to the standard output and exit.

       -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.

       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.

SEE ALSO
       vi(1), sudoers(4), sudo(1m), vipw(1m)

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

        Todd Miller

       See the CONTRIBUTORS file in the sudo distribution
       (http://www.sudo.ws/sudo/contributors.html) for a list of people who
       have contributed to sudo.

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.



1.8.4                           March 12, 2012                      VISUDO(1m)
