NAME

     visudo — edit the sudoers file

SYNOPSIS

     visudo [-chOPqsV] [[-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, performs basic validity checks, and checks for syntax errors before
     installing the edited file.  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 syntax error, so will sudo.  If ‘e’ is
     typed to edit the sudoers file after a syntax 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 sudo does not preserve
               the SUDO_EDITOR, VISUAL, or EDITOR environment variables unless they are present in the env_keep
               list or the env_reset option is disabled in the sudoers file.  The default editor path is
               /usr/bin/editor 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 visudo is typically run as root so
               this option may allow a user with visudo privileges to run arbitrary commands as root without
               logging.  An alternative is to place a colon-separated list of “safe” editors int the editor
               variable.  visudo will then only use SUDO_EDITOR, VISUAL, or EDITOR if they match a value
               specified 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 function
               when visudo is invoked via sudo.  The default value is on, which can be set at compile time via
               the --with-env-editor configure 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 path to the sudoers file was not specified, visudo will also
                 check the file ownership and permissions (see the -O and -P options).  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, see below.  As of version 1.8.27, the sudoers path
                 can be specified without using the -f option.

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

     -O, --owner
                 Enforce the default ownership (user and group) of the sudoers file.  In edit mode, the owner of
                 the edited file will be set to the default.  In check mode (-c), an error will be reported if
                 the owner is incorrect.  This option is enabled by default if the sudoers file was not
                 specified.

     -P, --perms
                 Enforce the default permissions (mode) of the sudoers file.  In edit mode, the permissions of
                 the edited file will be set to the default.  In check mode (-c), an error will be reported if
                 the file permissions are incorrect.  This option is enabled by default if the sudoers file was
                 not specified.

     -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 syntax 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.

     A sudoers file may be specified instead of the default, /etc/sudoers.  The temporary file used is the
     specified sudoers file with “.tmp” appended to it.  In check-only mode only, ‘-’ may be used to indicate
     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.

   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, user-ID, group-ID, 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=user-ID
               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=group-ID
               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          Default temporary file used by visudo

DIAGNOSTICS

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

     sudoers file busy, try again later.
           Someone else is currently editing the sudoers file.

     /etc/sudoers: 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.

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 complete details.