visudo
—
edit the sudoers file
visudo |
[ -chqsV ]
[-f
sudoers ] |
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.
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 variables are not
preserved by default when the env_reset
sudoers option is enabled. The default editor
path is 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 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 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
-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,
/usr/local/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 letters,
digits, and the underscore (‘_
’)
character.
-V
,
--version
- Print the
visudo
and
sudoers grammar versions and exit.
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.
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
- /usr/local/etc/sudo.conf
- Sudo front end configuration
- /usr/local/etc/sudoers
- List of who can run what
- /usr/local/etc/sudoers.tmp
- Lock file for visudo
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.
/usr/local/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 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 file in the
sudo
distribution (https://www.sudo.ws/contributors.html) 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 feel you have found a bug in
visudo
,
please 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 file distributed with
sudo
or https://www.sudo.ws/license.html
for complete details.