VISUDO(8) System Manager's Manual VISUDO(8)
NAME
visudo — edit the sudoers file
SYNOPSIS
visudo [-chIOPqsV] [[-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, per-
forms basic validity checks, and checks for syntax errors before in-
stalling the edited file. If the sudoers file is currently being edited
you will receive a message to try again later.
If the sudoers file does not exist, it will be created unless the editor
exits without writing to the file.
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 syn-
tax 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 dis-
abled 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 alterna-
tive 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 config-
ure 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 op-
tions). A message will be printed to the standard output de-
scribing the status of sudoers unless the -q option was speci-
fied. 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-ex-
isting syntax error. By default, visudo will edit the main
sudoers file and any files included via @include or #include di-
rectives. 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 de-
fault 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 ref-
erenced but not actually defined or if there is a cycle in an
alias, visudo will consider this a syntax error. It is not pos-
sible 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” ap-
pended 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.
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, 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 argu-
ments 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.
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 if SUDO_EDITOR is not set
EDITOR Used by visudo if neither SUDO_EDITOR nor VISUAL is set
FILES
/etc/sudo.conf Sudo front-end configuration
/etc/sudoers List of who can run what
/etc/sudoers.tmp Default temporary file used by visudo
DIAGNOSTICS
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 er-
rors, 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 mes-
sage 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 cy-
cles when parsing the sudoers file.
ignoring editor backup file
While processing a @includedir or #includedir, a file was found
with a name that ends in ‘~’ or .bak. Such files are skipped by
sudo and visudo.
ignoring file name containing '.'
While processing a @includedir or #includedir, a file was found
with a name that contains a ‘.’ character. Such files are skipped
by sudo and visudo.
unknown defaults entry "name"
The sudoers file contains a Defaults setting not recognized by
visudo.
SEE ALSO
vi(1), sudo.conf(5), sudoers(5), sudo(8), vipw(8)
AUTHORS
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 peo-
ple 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 believe you have found a bug in visudo, you can either file a bug
report in the sudo bug database, https://bugzilla.sudo.ws/, or open an
issue at https://github.com/sudo-project/sudo/issues. If you would pre-
fer to use email, messages may be sent to the sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public) or
<sudo@sudo.ws> (private).
Please not report security vulnerabilities through public GitHub issues,
Bugzilla or mailing lists. Instead, report them via email to
<Todd.Miller@sudo.ws>. You may encrypt your message with PGP if you
would like, using the key found at https://www.sudo.ws/dist/PGPKEYS.
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, in-
cluding, 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.
Sudo 1.9.16p2 July 27, 2023 VISUDO(8)
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