Ext4 file system (4th extended file system) is the next generation of journaling file systems, retaining backward compatibility with the previous file system, ext3. Ext4 was released as a functionally complete and stable filesystem in Linux kernel 2.6.28. Ubuntu 9.04 aka Jaunty Jackalope was released with support for the ext4 file system, so do many latest builds of many other Linux distributions.
