How to Boot your Para XEN DomU in Rescue Mode
On the XEN virtualization, there may be few problems related to your DomU and can not be fixed by mounting domU disks on dom0, then you need to boot the domU in rescue mode.
Normally whenever you need to boot the RHEL machine in rescue mode, you do it by using CD-ROM/DVD/PXE/NFS/FTP but para virtualization doesn’t support CD-ROM/DVD/PXE to boot it hence you need NFS/FTP/http bootable image to boot the machine.
Hence let’s start from here to boot the DomU from CD Image and get recue mode.
- Let suppose you have a CD/DVD iso on the server.
- Mount the image mount –t iso9660 –o loop /path/to/image/file.iso /mnt
- copy the vmlinuz and initrd.img from /mnt/isolinux/xen/ to another location /etc/xen/boot/
Lets suppose you have domain named “domain1“ and need to boot this domain in rescue mode.
Edit/update the domain1 configuration file /etc/xen/domain1 as follows.
- kernel = “/etc/xen/boot/vmliuz”
- ramdisk = “/etc/xen/boot/initrd.img”
- extra = “rescue”
Comment the bootloader line in your configuration
- Now create your domain as # xm create –c domain1
- It will ask you few questions and then linux image location on the domU disks
Hence you need to create NFS/FTP for the same to provide the image.
Lets start using NFS.
update /etc/exports with the following
/mnt *(ro,sync)
service portmap start
service nfs start
If you already running NFS there then just # exportfs –a
Now start again from step 5 to create the domain.
After creating domain it will ask you the way of booting then please choose NFS and then it will ask you for your IP setting which you know better.
Update the NFS server name : IP address of your Dom0
Shared name: /mnt
Now your domU is booting in rescue mode and you will get a shell a shell.
After fixing the problem, revert back the changes in the domain1 configuration file.
Please let me know if you have any question.
