What Filesystem to use for Linux Ubuntu?

I'm pretty sure ext3 is the default, but I've used ext4 for years with no troubles at all. ext4 is made to increase storage size and increase performance of the filesystem. Overall, I've had really good success with it.

This will tell you all you need to know about ext4, but I do recommend using it.

edit: ext4 IS stable according to the kernel.

If you don't have a good reason (based on a technical argument that you understand at least superficially), go with the default.

Ubuntu's default filesystem is ext4, since 9.10. Ext4 is an evolution of ext3, which was the default filesystem before. Ext4 is often noticeably faster than Ext3 even for ordinary desktop use.

Absolutely usable at home, even for beginners: ext2, ext3, ext4

Usable at home, rarely with issues: xfs (rarity is extreme rarity), jfs, reiserfs

Usable at home, frequently with issues: btrfs, and yeah, ye olde ntfs and fat (one should never ever use those two on Linux, but who knows?)

Not usable at home: zfs

Ext2 is old, but supported everywhere. For desktop/home server usage, ext3 and ext4 are almost completely equal, both are following the same principles and philosophy. The main difference is the level of maturity: ext4 isn't mature enough, so gigantic production systems don't use it yet (rare instabilities or performance issues might 'ruin' those systems [at least financially :)], but not yours). XFS does have a great performance when a lot of small files are moving (but don't use it in your boot partition - AFAIK it is still not supported officially by GRUB, although, I use it with Debian stable, and it works); JFS and ReiserFS aren't native old-school Linux filesystems, but their integration is more than enough. Btrfs is an emerging brilliant thought, always use it with working backup! From btrfs most distros can't boot now, but the support grows from kernel to kernel. Zfs is not yet for home usage, desktops never could use its functionality by its extreme limits (it is constructed for unreachable limits).

I've used btrfs on Ubuntu 10.10 and it was incredible slow (first thought my computer would be the problem). After reinstalling with ext4, it was much faster.