One of the important changes not listed in the feature list for Fedora 15 is Btrfs in Fedora 15. Anaconda, the Fedora installer has marked Btrfs as a supported filesystem in Rawhide, the Fedora development branch a while back. Btrfs integration is a long process in Fedora spanning several releases and will eventually result in Btrfs becoming the default filesystem in a couple of releases . Let’s look at what has been done so far:
* Eric Sandeen, Ext4 developer upstream and for Red Hat submitted a patch to Anaconda in January 2009 that allows users to use Btrfs as one of the filesystems and format their partitions with the installer if you explicitly pass a option “icantbelieveitsnotbtr” . It was documented and announced in Fedora 11 Alpha release. Just in case, this is not obvious, it was a bit of a joke but served the purpose of making it harder to actually pick this option and conveyed to the users this wasn’t a serious choice yet. It was definitely and clearly a experimental option
* In Fedora 13, the next step was taken with a integration of a yum plugin that supports Btfs snapshotting feature. Everytime you install or remove packages, this plugin will take a snapshot and allows you to rollback and restore from any software changes. yum history undo does a pretty good job in many cases but filesystem level undo is quite useful too. You only had to pass “btrfs” as a installation option in this release but it was still considered experimental
* In Fedora 15, you don’t need to pass any option. Btrfs will be one of the options by default but do note that Live images don’t support anything other than the default of Ext4 still.
The future plan for Btrfs in Fedora has been detailed out by Josef Basik, Red Hat Btrfs filesystem developer. Josef is planning on adding Btrfs support into GRUB 2 as well but Grub 0.97, the legacy version is what Fedora is using by default and although the repository does have a grub2 package for users wanting to try it out, more work needs to be driven by someone interested in this effort in Fedora to make GRUB 2 the default. Fedora 17 or later would have this filesystem by default if things go according to plan but I fully intend to migrate to Btrfs as my root filesystem for Fedora 15 if it finally gets a fsck that can actually repair damage instead of just reporting it which is indeed part of the Fedora plan. One of the interesting projects to keep an eye on is snap, a project to provide desktop integration of Btrfs and I would really love to see seamless integration with file managers like Nautilus. The future is butter and it is better.