VISUDO(8) BSD System Manager's Manual VISUDO(8)
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, per-
forms 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 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 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 /bin/vi 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 vari-
able. 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 environ-
ment 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 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, 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 speci-
fied, 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 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 under-
score (`_') 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.
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 com-
plete details.
Sudo 1.9.5p2 August 27, 2020 Sudo 1.9.5p2
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