VISUDO(8)

NAME

visudo - edit the sudoers file

SYNOPSIS

visudo [-c] [-q] [-s] [-V] [-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.

There is a hard-coded list of editors that visudo will use set at compile-time that may be overridden via the editor sudoers Default variable. On Debian systems, this list defaults to /usr/bin/editor,
which is meant to be a system-wide default editor chosen through the
alternatives system. 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.
Despite this potential risk, sudo on Debian is compiled with the
--with-env-editor flag.

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).

OPTIONS

visudo accepts the following command line options:

-c Enable check-only mode. The existing sudoers file will be
checked for syntax and a message will be printed to the
standard output detailing the status of sudoers. If the syntax check completes successfully, visudo will exit with a value of 0. If a syntax error is encountered, visudo will exit with a value of 1.
-f sudoers Specify and 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.
-q 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 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 hostname or username that consists
solely of uppercase letters, digits, and the underscore
('_') character.
-V The -V (version) option causes visudo to print its version
number and exit.

ENVIRONMENT

The following environment variables may be consulted depending on the
value of the editor and env_editor sudoers variables:

VISUAL Invoked by visudo as the editor to use

EDITOR Used by visudo if VISUAL is not set

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 userid 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 undeclare
{User,Runas,Host,Cmnd}_Alias or you have a user or hostname 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.

SEE ALSO

vi(1), sudoers(5), sudo(8), vipw(8)

AUTHOR

Many people have worked on sudo over the years; this version of visudo was written by:
Todd Miller
See the HISTORY file in the sudo distribution or visit
http://www.sudo.ws/sudo/history.html for more details.

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.
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