convert ext3 to ext4

I’ve successfully done this on my root fs:
I’ve no boot partition (my system is debian squeeze own compiled kernel 2.6.29.1)

tune2fs -O extents,uninit_bg,dir_index /dev/DEV

e2fsck -fDy /dev/DEV

vim /etc/mtab
vim /etc/fstab

You only need the newest Knoppix v6; boot it and do the above commands

Only use under debian grub-pc
Grub-0.97 is not able to boot from ext4