trying to convert a live root ext3 filesystem to ext4

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http://serverfault.com – I am trying to convert a root ext3 filesystem to ext4. So i ran tune2fs -O extents,uninit_bg,dir_index /dev/sda1 Then I changed the filesystem type from ext3 to ext4 in /etc/fstab and then added rootfstype to the grub config files. I've rebooted assuming that the kernel would just fsck on its own but it hasn't come up (headless remote machine). Is this just a matter of getting fsck to run or is there something else I need to do? (HowTos)