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VISUDO(8)		  BSD System Manager's Manual		     VISUDO(8)

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(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/bin/editor.	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 con‐
     figured with the --with-env-editor option or the env_editor Default vari‐
     able 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 let‐
		 ters, 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(5) 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 speci‐
     fied, 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(5), 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 under‐
	   score (‘_’) 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 mes‐
	   sage 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(5), sudoers(5), sudo(8), vipw(8)

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, includ‐
     ing, 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 1.8.21p2		       February 22, 2017		 Sudo 1.8.21p2
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