Visudo Manual
NAME
visudo
—
edit the sudoers file
SYNOPSIS
visudo |
[-chqsV ] [-f
sudoers] [-x
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
vi
. 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
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
file,--export
=file- Export sudoers in JSON format and write it to
file. If file is
‘
-
’, the exported sudoers policy will to be written to the standard output. The exported format is intended to be easier for third-party applications to parse that the traditional sudoers format. The various values have explicit types which removes much of the ambiguity of the sudoers format.
ENVIRONMENT
The following environment variables may be consulted depending on the value of the editor and env_editor sudoers settings:
FILES
- /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. In
-s
(strict) mode this is an error, not a warning. 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.
SEE ALSO
AUTHORS
Many people have worked on sudo
over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS file in the sudo
distribution (http://www.sudo.ws/sudo/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
http://www.sudo.ws/sudo/bugs/
SUPPORT
Limited free support is available via the sudo-users mailing list, see http://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 http://www.sudo.ws/sudo/license.html for
complete details.