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.
There is a hard-coded list of one or more editors that
visudo will use
set at compile-time that may be overridden via the
editor
sudoers Default variable. This list defaults to
"/usr/local/bin/vi". 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.
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 errors, 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
- 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. In check-only mode only, the argument to -f may be
"-", indicating that sudoers will be read from the
standard input.
- -h
- The -h (help) option causes visudo to
print a short help message to the standard output and exit.
- -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 host name or user name 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 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). 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.
- 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. This
is only a warning by default as sudo will ignore cycles when
parsing the sudoers file.
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 CONTRIBUTORS file in the
sudo distribution
(
http://www.sudo.ws/sudo/contributors.html) for a 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
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.