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
used before it is defined, 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
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.
Can't find you in the passwd database
Your user ID does not appear in the system passwd file.
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). 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. 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. This is
only a warning by default as sudo will ignore cycles when parsing
the sudoers file.
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 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.
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