visudo —
edit
the sudoers file
visudo |
[-chIOPqsV]
[[-f]
sudoers] |
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.
-
-I,
--no-includes
- Disable the editing of include files unless there is a
pre-existing syntax error. By default, visudo
will edit the main sudoers file and any
files included via @include or
#include directives. Files included via
@includedir or
#includedir are never edited unless they
contain a syntax error.
-
-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.
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.
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
- /etc/sudo.conf
- Sudo front-end configuration
- /etc/sudoers
- List of who can run what
- /etc/sudoers.tmp
- Default temporary file used by visudo
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.
vi(1),
sudo.conf(5),
sudoers(5),
sudo(8),
vipw(8)
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.
There is no easy way to prevent a user from gaining a root shell if the editor
used by
visudo allows shell escapes.
If you believe you have found a bug in
visudo, you
can submit a bug report at
https://bugzilla.sudo.ws/
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.
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.