visudo - Unix, Linux Command
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. This list defaults to the path to vi(1) on
your system, as determined by the configure script. 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-enveditor
flag 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:
| Tag | Description |
|---|
|
-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
|
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 flag.
|
|
-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 are used only if
visudo
was configured with the
--with-env-editor option:
| Tag | Description |
|---|
|
VISUAL
|
Invoked by visudo as the editor to use
|
|
EDITOR
|
Used by visudo if VISUAL is not set
|
FILES
| Tag | Description |
|---|
|
/etc/sudoers
|
List of who can run what
|
|
/etc/sudoers.tmp
|
Lock file for visudo
|
DIAGNOSTICS
| Tag | Description |
|---|
|
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: undeclared Alias referenced near ...
|
Either you are using a {User,Runas,Host,Cmnd}_Alias before
defining it or you have a user or hostname listed that
consists solely of uppercase letters, digits, and the
underscore (’_’) character. If the latter, you can ignore
the warnings (sudo will not complain). In -s (strict)
mode these are errors, not warnings.
|
|
Warning: runas_default set after old value is in use ...
|
You have a runas_default Defaults setting listed in the sudoers
file after its value has already been used. This means that entries
prior to the runas_default setting will match based on the default
value of runas_default (root) whereas entries
after the runas_default setting will match based on the new
value. This is usually unintentional and in most cases the
<runas_default> setting should be placed before any Runas_Alias
or User specifications. 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:
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.
