A while back, I started experimenting with Ubuntu after playing with Fedora. I decided to jump to Ubuntu and needed to move data from the Fedora-managed logical volume to Ubuntu. Here's what I did.
$ sudo apt-get install lvm2
$ sudo modprobe dm-mod
$ sudo vgscan
$ sudo vgchange -ay VolGroup00
$ sudo lvs
$ sudo mkdir /mnt/fcroot
$ sudo mount /dev/VolGroup00/LogVol00 /mnt/fcroot -o ro,user