table of contents
VISUDO(8) | 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, 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 withvisudo
.visudo
will choose the editor that matches the user'sSUDO_EDITOR
,VISUAL
orEDITOR
environment variable if possible, or the first editor in the list that exists and is executable. Note that theSUDO_EDITOR
,VISUAL
andEDITOR
environment variables 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
configure option. - env_editor
- If set,
visudo
will use the value of theSUDO_EDITOR
,VISUAL
orEDITOR
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 useSUDO_EDITOR
,VISUAL
orEDITOR
if they match a value specified in editor. If the env_reset flag is enabled, theSUDO_EDITOR
,VISUAL
and/orEDITOR
environment variables must be present in the env_keep list for the env_editor flag to function whenvisudo
is invoked viasudo
. 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, /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.
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
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.
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
ifSUDO_EDITOR
is not set EDITOR
- Used by
visudo
if neitherSUDO_EDITOR
norVISUAL
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 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 assudo
will ignore cycles when parsing the sudoers file. unknown defaults entry "name"
- The sudoers file contains a
Defaults
setting not recognized byvisudo
.
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 (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
complete details.
January 26, 2018 | Sudo 1.8.23 |