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

NAME
     visudo -- edit the sudoers file

SYNOPSIS
     visudo [-chqsV] [-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, 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.

     visudo parses the sudoers file after editing 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 caution 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).

     There are two sudoers settings that determine which editor visudo will
     run.

     editor    A colon (`:') separated list of editors allowed to be used with
	       visudo.	visudo will choose the editor that matches the user's
	       SUDO_EDITOR, VISUAL or EDITOR environment variable if possible,
	       or the first editor in the list that exists and is executable.
	       Note that the SUDO_EDITOR, VISUAL and EDITOR environment vari-
	       ables are not preserved by default when the env_reset sudoers
	       option is enabled.  The default editor path is /bin/vi which
	       can be set at compile time via the --with-editor configure
	       option.

     env_editor
	       If set, visudo will use the value of the SUDO_EDITOR, VISUAL or
	       EDITOR environment variables before falling back on the default
	       editor list.  Note that this may create a security hole as it
	       allows the user to run any arbitrary command as root without
	       logging.	 A safer alternative is to place a colon-separated
	       list of editors in the editor variable.	visudo will then only
	       use SUDO_EDITOR, VISUAL or EDITOR if they match a value speci-
	       fied in editor.	If the env_reset flag is enabled, the
	       SUDO_EDITOR, VISUAL and/or EDITOR environment variables must be
	       present in the env_keep list for the env_editor flag to func-
	       tion when visudo is invoked via sudo.  The default value is on,
	       which can be set at compile time via the --with-env-editor con-
	       figure option.

     The options are as follows:

     -c, --check
		 Enable check-only mode.  The existing sudoers file (and any
		 other files it includes) will be checked for syntax errors.
		 If the -f option has not been specified, visudo will also
		 check the sudoers file 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.
		 Because the policy is evaluated in its entirety, it is not
		 sufficient to check an individual sudoers include file for
		 syntax errors.

     -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.

   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:

     SUDO_EDITOR      Invoked by visudo as the editor to use

     VISUAL	      Used by visudo if SUDO_EDITOR is not set

     EDITOR	      Used by visudo if neither SUDO_EDITOR nor VISUAL is 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.

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,
     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 com-
     plete details.

Sudo 1.8.23		       January 26, 2018			   Sudo 1.8.23