This is just a simple tip to use ext4 filesystems in Ubuntu Intrepid Ibex 8.10.
In Ubuntu Jaunty ext4 filesystems is fully supported but in Intrepid was in developing.
To use it we must load the module ext4dev

sudo modprobe ext4dev

to check the filesystems supported by the kernel we can do

cat /proc/filesystems

there should be a line with ext4dev.
Now, if we try to mount a formatted partition as ext4, will see that we can not do

sudo dmesg | tail

shows a line that says

EXT4-fs: sda2: not marked OK to use with test code.

to solve it we need to enable test_fs, an extended option for ext4 partitions

sudo tune2fs -E test_fs /dev/sda1

Now, we can mount it without problems

sudo mount -t ext4dev /dev/sda1 /mnt/disk

That’s all folks!

Note 1: replace sda1 by the appropiate device
Note 2: sorry for my english :)