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, pro-
vides 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.
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 the SUDO_EDITOR, VISUAL and EDITOR environment vari-
ables are not preserved by default when the env_reset sudoers
option is enabled. The default editor path is /usr/bin/vi
which can be set at compile time via the --with-editor config-
ure 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 this may create a security hole as it
allows the user to run any arbitrary command as root without
logging. A safer alternative is to place a colon-separated
list of editors in the editor variable. visudo will then only
use SUDO_EDITOR, VISUAL or EDITOR if they match a value speci-
fied 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 func-
tion when visudo is invoked via sudo. The default value is on,
which can be set at compile time via the --with-env-editor con-
figure 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 -f option has not been specified, visudo will also
check the sudoers 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. 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.
Because the policy is evaluated in its entirety, it is not
sufficient to check an individual sudoers include file for
syntax errors.
-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 let-
ters, digits, and the underscore (`_') character.
-V, --version
Print the visudo and sudoers grammar versions and exit.
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 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 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 1.8.23 January 26, 2018 Sudo 1.8.23
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