Add 'virt-rescue' command.

This command runs a "rescue appliance" against a virtual machine
or disk image.  This is useful for making ad-hoc interactive
changes to virtual machines.

  $ virt-rescue --ro /dev/vg_trick/F11x64

  Welcome to virt-rescue, the libguestfs rescue shell.

  Note: The contents of / are the rescue appliance.
  You have to mount the guest's partitions under /sysroot
  before you will be able to examine them.

  bash: cannot set terminal process group (-1): Inappropriate ioctl for device
  bash: no job control in this shell
  ><rescue> mount /dev/vg_f11x64/lv_root /sysroot
  EXT4-fs (dm-0): barriers enabled
  kjournald2 starting: pid 269, dev dm-0:8, commit interval 5 seconds
  EXT4-fs (dm-0): internal journal on dm-0:8
  EXT4-fs (dm-0): delayed allocation enabled
  EXT4-fs: file extents enabled
  EXT4-fs: mballoc enabled
  EXT4-fs (dm-0): mounted filesystem with ordered data mode
  ><rescue> ls /sysroot/
  bin   dev  home  lib64       media  opt   root  selinux  sys  usr
  boot  etc  lib   lost+found  mnt    proc  sbin  srv      tmp  var
  ><rescue> exit

1 files changed, 169 insertions, 0 deletions

diff --git a/rescue/virt-rescue.pl b/rescue/virt-rescue.pl
new file mode 100755
index 00000000..a44940d5
--- /dev/null
+++ b/rescue/virt-rescue.pl
@@ -0,0 +1,169 @@
+#!/usr/bin/perl -w
+# virt-rescue
+# Copyright (C) 2009 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+use warnings;
+use strict;
+
+use Sys::Guestfs;
+use Sys::Guestfs::Lib qw(open_guest);
+use Pod::Usage;
+use Getopt::Long;
+use Locale::TextDomain 'libguestfs';
+
+=encoding utf8
+
+=head1 NAME
+
+virt-rescue - Run a rescue shell on a virtual machine
+
+=head1 SYNOPSIS
+
+ virt-rescue [--options] domname
+
+ virt-rescue [--options] disk.img [disk.img ...]
+
+=head1 DESCRIPTION
+
+virt-rescue gives you a rescue shell and some simple recovery tools
+which you can use on a virtual machine disk image.
+
+After running virt-rescue, what you see under C</> is the recovery
+appliance.  You must mount the virtual machine's filesystems by hand,
+eg:
+
+ # lvs
+ LV      VG        Attr   LSize   Origin Snap%  Move Log Copy%  Convert
+ lv_root vg_f11x64 -wi-a-   8.83G
+ lv_swap vg_f11x64 -wi-a- 992.00M
+ # mount /dev/vg_f11x64/lv_root /sysroot
+ # ls /sysroot
+
+B<Note> that the virtual machine must not be powered on when you use
+this tool.  Doing so will probably result in disk corruption in the
+VM.  However if you use the I<--ro> (read only) option, then you can
+attach a shell to a running machine, but the results might be strange
+or inconsistent.
+
+This tool is just designed for quick interactive hacking on a virtual
+machine.  For more structured access to a virtual machine disk image,
+you should use L<guestfs(3)>.  To get a structured shell, use
+L<guestfish(1)>.
+
+=head1 OPTIONS
+
+=over 4
+
+=cut
+
+my $help;
+
+=item B<--help>
+
+Display brief help.
+
+=cut
+
+my $version;
+
+=item B<--version>
+
+Display version number and exit.
+
+=cut
+
+my $uri;
+
+=item B<--connect URI> | B<-c URI>
+
+If using libvirt, connect to the given I<URI>.  If omitted, then we
+connect to the default libvirt hypervisor.
+
+If you specify guest block devices directly, then libvirt is not used
+at all.
+
+=cut
+
+my $readonly;
+
+=item B<--ro> | B<-r>
+
+Open the image read-only.
+
+=back
+
+=cut
+
+GetOptions ("help|?" => \$help,
+            "version" => \$version,
+            "connect|c=s" => \$uri,
+	    "ro|r" => \$readonly,
+    ) or pod2usage (2);
+pod2usage (1) if $help;
+if ($version) {
+    my $g = Sys::Guestfs->new ();
+    my %h = $g->version ();
+    print "$h{major}.$h{minor}.$h{release}$h{extra}\n";
+    exit
+}
+
+pod2usage (__"virt-rescue: no image or VM names rescue given")
+    if @ARGV == 0;
+
+my @args = (\@ARGV);
+push @args, address => $uri if $uri;
+push @args, rw => 1 unless $readonly;
+my $g = open_guest (@args);
+
+$g->set_direct (1);
+$g->set_append ("guestfs_rescue=1");
+
+$g->launch ();
+
+exit 0;
+
+=head1 SEE ALSO
+
+L<guestfs(3)>,
+L<guestfish(1)>,
+L<virt-cat(1)>,
+L<Sys::Guestfs(3)>,
+L<Sys::Guestfs::Lib(3)>,
+L<Sys::Virt(3)>,
+L<http://libguestfs.org/>.
+
+=head1 AUTHOR
+
+Richard W.M. Jones L<http://et.redhat.com/~rjones/>
+
+=head1 COPYRIGHT
+
+Copyright (C) 2009 Red Hat Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.