Converting from a standard ext2 disk format to a journalled ext3
format is easy, since it simply involves adding a journal file. It can
be done while the system is running with:
# tune2fs -j /dev/hda1
Then change ext2 to ext3 in /etc/fstab and unmount/mount for
it to take effect. If /dev/hda is your root partition, then
you'll need to reboot for it to take effect.