visudo - edit the sudoers file
visudo [ -c ] [ -f sudoers ] [ -q ] [ -s ] [ -V ]
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 EDITOR or
VISUAL environment variables unless they contain an editor
in the aforementioned editors list. However, if visudo is
configured with the --with-enveditor flag or the enveditor
Default variable is set in sudoers, visudo will use any
the editor defines by EDITOR or VISUAL. Note that this
can be a security hole since it allows the user to execute
any program they wish simply by setting EDITOR or VISUAL.
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).
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 Specify and alternate sudoers file location. With
this option visudo will edit (or check) the sudoers
file of your choice, instead of the default,
@sysconfdir@/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.
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.
The following environment variables are used only if
visudo was configured with the --with-env-editor option:
EDITOR Invoked by visudo as the editor to
use
VISUAL Used Invoked visudo if EDITOR is
not set
/etc/sudoers List of who can run what
/etc/sudoers.tmp Lock file for visudo
Many people have worked on sudo over the years; this version
of visudo was written by:
Todd Miller <[email protected]>
See the HISTORY file in the sudo distribution or visit
http://www.sudo.ws/sudo/history.html for more details.
If you feel you have found a bug in sudo, please submit a
bug report at http://www.sudo.ws/sudo/bugs/
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 for complete details.
There is no easy way to prevent a user from gaining a root
shell if the editor used by visudo allows shell escapes.
vi(1), sudoers(5), sudo(8), vipw(8)
1.6.7 March 13, 2003 3 [ Back ] | 