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/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. 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,
/private/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
- /private/etc/sudo.conf
- Sudo front-end configuration
- /private/etc/sudoers
- List of who can run what
- /private/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.
- /private/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.