This is my first post in english. I am sorry if there are some mistakes – it is not my native language

Recently I had to rename volume group in one of my virtual machines. It is based on CentOS (both dom0 and domU) and it was paravirtualized. I couldn`t do it on running system because root partition was on logical volume. I had to boot the machine in rescue mode. I had no idea how to boot from CD/DVD iso image – AFAIK it is impossible on pv guests. I had to boot vm directly from kernel and initrd used in installation (both are xen aware). So I copied  them to /tmp/xen from /images/xen/ on CD/DVD installation disc.

Then I had to comment out the following line from vm`s config file to bypass pygrub bootloader:

#bootloader = "/usr/bin/pygrub"


Now I needed to tell my vm to use kernel and initrd I had previously copied so I added the following lines:

kernel = "/tmp/xen/vmlinuz"
ramdisk = "/tmp/xen/initrd.img"
extra = "rescue method=http://192.168.0.2/install/centos/"


The last line passes extra arguments to kernel. There is a rescue keyword and a method which tells anaconda installer to get install files from my http server.

After that I was able to boot vm in rescue and rename my LVM virtual group.