=cut
Copyright (c) 1996,1998-2002 Todd C. Miller <Todd.Miller@courtesan.com>
All rights reserved.
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modification, are permitted provided that the following conditions
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$Sudo: visudo.pod,v 1.28 2002/01/12 22:55:01 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), sudo(8), vipw(8).