VISUDO(1m)                   System Manager's Manual                  VISUDO(1m)

NAME
     visudo - edit the sudoers file

SYNOPSIS
     visudo [-chqsV] [-f sudoers] [-x output_file]

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 run 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
                 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, --strict
                 Enable strict checking of the sudoers file.  If an alias is
                 referenced but not actually defined or if there is a cycle in
                 an alias, 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, --version
                 Print the visudo and sudoers grammar versions and exit.

     -x output_file, --export=output_file
                 Export a sudoers in JSON format and write it to output_file.
                 If output_file is `-', the exported sudoers policy will be
                 written to the standard output.  By default, /etc/sudoers
                 (and any files it includes) will be exported.  The -f option
                 can be used to specify a different sudoers file to export.
                 The exported format is intended to be easier for third-party
                 applications to parse than the traditional sudoers format.
                 The various values have explicit types which removes much of
                 the ambiguity of the sudoers format.

   Debugging and sudoers plugin arguments
     visudo versions 1.8.4 and higher support a flexible debugging framework
     that is configured via Debug lines in the sudo.conf(4) file.

     Starting with sudo 1.8.12, visudo will also parse the arguments to the
     sudoers plugin to override the default sudoers path name, UID, GID and
     file mode.  These arguments, if present, should be listed after the path
     to the plugin (i.e. after sudoers.so).  Multiple arguments may be
     specified, separated by white space.  For example:

           Plugin sudoers_policy sudoers.so sudoers_mode=0400

     The following arguments are supported:

     sudoers_file=pathname
               The sudoers_file argument can be used to override the default
               path to the sudoers file.

     sudoers_uid=uid
               The sudoers_uid argument can be used to override the default
               owner of the sudoers file.  It should be specified as a numeric
               user ID.

     sudoers_gid=gid
               The sudoers_gid argument can be used to override the default
               group of the sudoers file.  It must be specified as a numeric
               group ID (not a group name).

     sudoers_mode=mode
               The sudoers_mode argument can be used to override the default
               file mode for the sudoers file.  It should be specified as an
               octal value.

     For more information on configuring sudo.conf(4), please refer to its
     manual.

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/sudo.conf            Sudo front end configuration

     /etc/sudoers              List of who can run what

     /etc/sudoers.tmp          Lock file for visudo

DIAGNOSTICS
     In addition to reporting sudoers parse errors, visudo may produce the
     following messages:

     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.

     you do not exist in the passwd database
           Your user ID does not appear in the system passwd database.

     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
           underscore (`_') character.  In the latter case, you can ignore the
           warnings (sudo will not complain).  The message is prefixed with
           the path name of the sudoers file and the line number where the
           undefined alias was used.  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.  The message is prefixed with the path name of the sudoers
           file and the line number where the unused alias was defined.  You
           may wish to comment out or remove the unused alias.

     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.  The
           message is prefixed with the path name of the sudoers file and the
           line number where the cycle was detected.  This is only a warning
           unless visudo is run in -s (strict) mode as sudo will ignore cycles
           when parsing the sudoers file.

     unknown defaults entry "name"
           The sudoers file contains a Defaults setting not recognized by
           visudo.

     /etc/sudoers: input and output files must be different
           The -x flag was used and the specified output_file has the same
           path name as the sudoers file to export.

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

AUTHORS
     Many people have worked on sudo over the years; this version consists of
     code written primarily by:

           Todd C. Miller

     See the CONTRIBUTORS file in the sudo distribution
     (https://www.sudo.ws/contributors.html) for an exhaustive 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
     https://bugzilla.sudo.ws/

SUPPORT
     Limited free support is available via the sudo-users mailing list, see
     https://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 https://www.sudo.ws/license.html for
     complete details.

Sudo 1.8.21                    February 22, 2017                   Sudo 1.8.21
