Provided by: sudo-ldap_1.9.11p3-1ubuntu1_amd64 
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. 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. 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 in 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. 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), 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.md file in the sudo distribution
(https://www.sudo.ws/about/contributors/) 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 believe you have found a bug in visudo, you can 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.md file distributed with sudo or
https://www.sudo.ws/about/license/ for complete details.