=cut
Copyright (c) 1996,1998-2003 Todd C. Miller <Todd.Miller@courtesan.com>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

3. The name of the author may not be used to endorse or promote products
   derived from this software without specific prior written permission
   from the author.

4. Products derived from this software may not be called "Sudo" nor
   may "Sudo" appear in their names without specific prior written
   permission from the author.

THIS SOFTWARE 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.  IN NO EVENT SHALL
THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Sponsored in part by the Defense Advanced Research Projects
Agency (DARPA) and Air Force Research Laboratory, Air Force
Materiel Command, USAF, under agreement number F39502-99-1-0512.

$Sudo: visudo.pod,v 1.31 2003/03/15 20:31:02 millert Exp $
=pod

=head1 NAME

visudo - edit the sudoers file

=head1 SYNOPSIS

B<visudo> [ B<-c> ] [ B<-f> I<sudoers> ] [ B<-q> ] [ B<-s> ] [ B<-V> ]

=head1 DESCRIPTION

B<visudo> edits the I<sudoers> file in a safe fashion, analogous to
vipw(8).  B<visudo> locks the I<sudoers> file against multiple
simultaneous edits, provides basic sanity checks, and checks
for parse errors.  If the I<sudoers> file is currently being
edited you will receive a message to try again later.

There is a hard-coded list of editors that B<visudo> will use set
at compile-time that may be overridden via the I<editor> I<sudoers>
C<Default> variable.  This list defaults to the path to vi(1) on
your system, as determined by the I<configure> script.  Normally,
B<visudo> does not honor the C<EDITOR> or C<VISUAL> environment
variables unless they contain an editor in the aforementioned editors
list.  However, if B<visudo> is configured with the I<--with-enveditor>
flag or the I<enveditor> C<Default> variable is set in I<sudoers>,
B<visudo> will use any the editor defines by C<EDITOR> or C<VISUAL>.
Note that this can be a security hole since it allows the user to
execute any program they wish simply by setting C<EDITOR> or C<VISUAL>.

B<visudo> parses the I<sudoers> file after the edit and will
not save the changes if there is a syntax error.  Upon finding
an error, B<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 I<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 B<visudo>
believes there to be a parse error, so will B<sudo> and no one
will be able to B<sudo> again until the error is fixed.
If "e" is typed to edit the  I<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).

=head1 OPTIONS

B<visudo> accepts the following command line options:

=over 4

=item -c

Enable B<check-only> mode.  The existing I<sudoers> file will be
checked for syntax and a message will be printed to the
standard output detailing the status of I<sudoers>.
If the syntax check completes successfully, B<visudo> will
exit with a value of 0.  If a syntax error is encountered,
B<visudo> will exit with a value of 1.

=item -f

Specify and alternate I<sudoers> file location.  With this option
B<visudo> will edit (or check) the I<sudoers> file of your choice,
instead of the default, @sysconfdir@/sudoers.  The lock file used
is the specified I<sudoers> file with ".tmp" appended to it.

=item -q

Enable B<quiet> mode.  In this mode details about syntax errors
are not printed.  This option is only useful when combined with
the B<-c> flag.

=item -s

Enable B<strict> checking of the I<sudoers> file.  If an alias is
used before it is defined, B<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.

=item -V

The B<-V> (version) option causes B<visudo> to print its version number
and exit.

=back

=head1 ERRORS

=over 4

=item sudoers file busy, try again later.

Someone else is currently editing the I<sudoers> file.

=item @sysconfdir@/sudoers.tmp: Permission denied

You didn't run B<visudo> as root.

=item Can't find you in the passwd database

Your userid does not appear in the system passwd file.

=item 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 (B<sudo> will not complain).  In B<-s> (strict)
mode these are errors, not warnings.

=back

=head1 ENVIRONMENT

The following environment variables are used only if B<visudo>
was configured with the I<--with-env-editor> option:

 EDITOR			Invoked by visudo as the editor to use
 VISUAL			Used Invoked visudo if EDITOR is not set

=head1 FILES

 @sysconfdir@/sudoers		List of who can run what
 @sysconfdir@/sudoers.tmp	Lock file for visudo

=head1 AUTHOR

Many people have worked on I<sudo> over the years; this version of
B<visudo> was written by:

 Todd Miller		<Todd.Miller@courtesan.com>

See the HISTORY file in the sudo distribution or visit
http://www.sudo.ws/sudo/history.html for more details.

=head1 BUGS

If you feel you have found a bug in sudo, please submit a bug report
at http://www.sudo.ws/sudo/bugs/

=head1 DISCLAIMER

B<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 B<sudo> for complete details.

=head1 CAVEATS

There is no easy way to prevent a user from gaining a root shell if 
the editor used by B<visudo> allows shell escapes.

=head1 SEE ALSO

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