Ubuntu 9.04 the "Jaunty Jackalope" was released today. It's got a lot of great new features including a new notification system on the desktop and support for cloud computing with full support for the Amazon EC2 API through the Eucalyptus project on the server.
One of the big features of this release is support for the recently released ext4 filesystem. Ext4 has a ton of great features and helps bring a modern filesystem implementation to Linux. One of the great features of ext4 is the ability to convert an existing ext3 filesystem to ext4 without losing any data. If you are thinking of upgrading your Ubuntu 8.10 machine to Ubuntu 9.04 and want to upgrade your filesystem as well, here's how to do it.
First you're going to want to upgrade your system from Ubuntu 8.10 to 9.04 if you haven't already done so. Follow the instructions here to perform the upgrade.
NOTE :: Make sure to back up all important data before upgrading the distribution or the filesystem
Next, boot the computer from the Ubuntu 9.04 Desktop CD Once you are booted into the live environment, run the following command replacing /dev/DEV with the drive partition that you want to upgrade.
tune2fs -O extents,uninit_bg,dir_index /dev/DEV
NOTE :: the -O is the capital letter O, not zero
You then need to run fsck to fix up some on-disk structures that tune2fs has modified.
e2fsck -fD /dev/DEV
Next, mount the drive
mount -t ext4 /dev/DEV /mnt
Edit fstab and change ext3 to ext4 on the drive you upgraded
UUID=xxxx / ext4 relatime,errors=remount-ro 0 1
Finally, you need to run grub-install on your new partition. The version of grub that shipped with Ubuntu 8.10 cannot boot from ext4 partitions so if you skip this step, your computer won't boot.
grub-install /dev/DEV --root-directory=/mnt --recheck
Now reboot the computer and enjoy your new ext4 filesystem.
NOTE :: By enabling the extents feature new files will be created in extents format, but this will not convert existing files to use extents. Non-extent files can be transparently read and written by Ext4.