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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | DIAGNOSTICS | SEE ALSO | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON |
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VISUDO(8) System Manager's Manual VISUDO(8)
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.
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 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,
/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.
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 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
/etc/sudo.conf Sudo front-end configuration
/etc/sudoers List of who can run what
/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.
/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.
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.
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 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 prefer
to use email, messages may be sent to the sudo-workers mailing
list, https://www.sudo.ws/mailman/listinfo/sudo-workers (public)
or <[email protected]> (private).
Please not report security vulnerabilities through public GitHub
issues, Bugzilla or mailing lists. Instead, report them via
email to <[email protected]>. You may encrypt your message
with PGP if you would like, using the key found at
https://www.sudo.ws/dist/PGPKEYS.
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.
This page is part of the sudo (execute a command as another user)
project. Information about the project can be found at
https://www.sudo.ws/. If you have a bug report for this manual
page, see ⟨https://bugzilla.sudo.ws/⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/sudo-project/sudo⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-08.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Sudo 1.9.16 July 27, 2023 VISUDO(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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