Provided by: sudo_1.8.31-1ubuntu1.5_amd64 
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, provides basic sanity checks, and checks for parse 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 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 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 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, 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.
-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.
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, 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(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 parse 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.
Sudo 1.8.31 October 20, 2019 VISUDO(8)