XEN: Directly attaching Xen DomU disk images to Dom0 for system rescue
This document (3312774) is provided subject to the disclaimer at the end of this document.
- Disk image backed DomU will not boot
- Access to files inside of a DomU disk image is needed
- Access via chroot inside of a DomU disk image is needed
The command "xm block-attach" is used to hot plug a disk to a DomU.
Command Syntax: xm block-attach
The backdev is the device/file that will be attached to the domain. You can use "file:""tap:aio","phy:" and others that Xen supports. It would be recommended to use the backend device specified in the configuration for the Xen DomU.
The frontdev device is where what the device will be presented to the domain as. In our example, we used "xvda", which is the first device. When attaching, you can see what devices are attached. This can be done using the "xm block-list 0" command.
mount and chroot
Once the disk has been attached, you may mount disk and follow normal rescue procedures.
- Discover the attached
diskfdisk -l /dev/xvda
- Mount the root file system. In
this TID, the root file system is on the second partition of
/dev/xvdamount /dev/xvda2 /mnt
- Check to make sure that the file system mount on /mnt is the one that you want
- Mount any other needed file
system under mount. Typical examples are /var and /homemount /dev/xvda3 /mnt/home
- "chroot" is a command that
changes the root for the current shell to the specific directory.
This is useful because all commands run under a chrooted
environment see the chrooted directory as root.chroot /mnt
- After you are done, exit the
- Unmount partitions on the disk
- If you are using LVM or EVMS
in Dom0 you may have to remove the device mapper mappingskpartx -d /dev/xvda
- Detach the disk from
Dom0xm block-detach 0 xvda
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- Document ID:3312774
- Creation Date:14-FEB-08
- Modified Date:27-APR-12
- SUSESUSE Linux Enterprise Server
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