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,
provides 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 configured with the --with-env-editor option or the
env_editor Default variable 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 letters, 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
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:
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 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 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 contrib-
uted 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 1.8.21p2 February 22, 2017 Sudo 1.8.21p2