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virt-rescue

NAME

virt-rescue - Run a rescue shell on a virtual machine

SYNOPSIS

  virt-rescue [--options] domname
 
  virt-rescue [--options] disk.img [disk.img ...]
 
 

WARNING

You must not use "virt-rescue" on live virtual machines. Doing so will probably result in disk corruption in the VM. "virt-rescue" tries to stop you from doing this, but doesn't catch all cases.

However if you use the --ro (read only) option, then you can attach a shell to a live virtual machine. The results might be strange or inconsistent at times but you won't get disk corruption.

DESCRIPTION

virt-rescue is like a Rescue CD, but for virtual machines, and without the need for a CD. virt-rescue gives you a rescue shell and some simple recovery tools which you can use to examine or rescue a virtual machine or disk image.

You can run virt-rescue on any virtual machine known to libvirt, or directly on disk image(s):

  virt-rescue GuestName
 
  virt-rescue --ro /path/to/disk.img
 
  virt-rescue /dev/sdc
 
 

For live VMs you must use the --ro option.

When you run virt-rescue on a virtual machine or disk image, you are placed in an interactive bash shell where you can use many ordinary Linux commands. What you see in "/" ("/bin", "/lib" etc) is the rescue appliance. You must mount the virtual machine's filesystems by hand. There is an empty directory called "/sysroot" where you can mount filesystems.

In the example below, we list logical volumes, then choose one to mount under "/sysroot":

  ><rescue> 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
  ><rescue> mount /dev/vg_f11x64/lv_root /sysroot
  ><rescue> ls /sysroot
 
 

If you don't know what filesystems are available on the virtual machine then you can use commands such as parted(8) and lvs(8) to find out.

NOTES

Virt-rescue can be used on any disk image file or device, not just a virtual machine. For example you can use it on a blank file if you want to partition that file (although we would recommend using guestfish(1) instead as it is more suitable for this purpose). You can even use virt-rescue on things like SD cards.

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 guestfs(3). To get a structured shell that you can use to make scripted changes to guests, use guestfish(1).

OPTIONS

--help

Display brief help.

--version

Display version number and exit.

--append kernelopts

Pass additional options to the rescue kernel.

--connect URI | -c URI

If using libvirt, connect to the given 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.

--memsize MB | -m MB

Change the amount of memory allocated to the rescue system. The default is set by libguestfs and is small but adequate for running system tools. The occasional program might need more memory. The parameter is specified in megabytes.

--ro | -r

Open the image read-only.

The option must always be used if the disk image or virtual machine might be running, and is generally recommended in cases where you don't need write access to the disk.

--selinux

Enable SELinux in the rescue appliance. You should read ``SELINUX'' in guestfs(3) before using this option.

ENVIRONMENT VARIABLES

Several environment variables affect virt-rescue. See ``ENVIRONMENT VARIABLES'' in guestfs(3) for the complete list.

SEE ALSO

guestfs(3), guestfish(1), virt-cat(1), Sys::Guestfs(3), Sys::Guestfs::Lib(3), Sys::Virt(3), <http://libguestfs.org/>.

AUTHOR

Richard W.M. Jones <http://people.redhat.com/~rjones/>

COPYRIGHT

Copyright (C) 2009-2010 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.