16.6.2. Running virt-rescue
Before you use
virt-rescue on a guest virtual machine, make sure the guest virtual machine is not running, otherwise disk corruption will occur. When you are sure the guest virtual machine is not live, enter:
virt-rescue GuestName
(where GuestName is the guest name as known to libvirt), or:
virt-rescue /path/to/disk/image
(where the path can be any file, any logical volume, LUN, or so on) containing a guest virtual machine disk.
You will first see output scroll past, as virt-rescue boots the rescue VM. In the end you will see:
Welcome to virt-rescue, the libguestfs rescue shell. Note: The contents of / are the rescue appliance. You have to mount the guest virtual machine's partitions under /sysroot before you can examine them. bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell ><rescue>
The shell prompt here is an ordinary bash shell, and a reduced set of ordinary Red Hat Enterprise Linux commands is available. For example, you can enter:
><rescue> fdisk -l /dev/vda
The previous command will list disk partitions. To mount a file system, it is suggested that you mount it under
/sysroot, which is an empty directory in the rescue machine for the user to mount anything you like. Note that the files under / are files from the rescue VM itself:
><rescue> mount /dev/vda1 /sysroot/ EXT4-fs (vda1): mounted filesystem with ordered data mode. Opts: (null) ><rescue> ls -l /sysroot/grub/ total 324 -rw-r--r--. 1 root root 63 Sep 16 18:14 device.map -rw-r--r--. 1 root root 13200 Sep 16 18:14 e2fs_stage1_5 -rw-r--r--. 1 root root 12512 Sep 16 18:14 fat_stage1_5 -rw-r--r--. 1 root root 11744 Sep 16 18:14 ffs_stage1_5 -rw-------. 1 root root 1503 Oct 15 11:19 grub.conf [...]
When you are finished rescuing the guest virtual machine, exit the shell by entering
exit or Ctrl+d.
virt-rescue has many command line options. The options most often used are:
- --ro: Operate in read-only mode on the guest virtual machine. No changes will be saved. You can use this to experiment with the guest virtual machine. As soon as you exit from the shell, all of your changes are discarded.
- --network: Enable network access from the rescue shell. Use this if you need to, for example, download RPM or other files into the guest virtual machine.
