Convert from ext3 to ext4

WARNING! Once you run following commands, the filesystem will no longer be mountable using the ext3. Please note that ext4 may have some bugs so do not use for production servers (wait for sometime watch Linux kernel mailing list for ext4 bugs). It’s recommended that you keep /boot in a ext3 partition for sometime.
You need ext4 patch applied into kernel and compile kernel with ext4 support. Once done type the following command to convert an existing ext3 filesystem to use ext4, type:

# tune2fs -O extents,uninit_bg,dir_index /dev/dev-name
For example convert /dev/sdb1 to ext4, enter:

# cd /; umount /dev/sdb1
# tune2fs -O extents,uninit_bg,dir_index /dev/sdb1
Next run fsck, enter:

# fsck -pf /dev/sdb1
How do I mount ext4 partition?
mount -t ext4 /dev/sdb1 /path
mount -t ext4 /dev/sdb1 /share
mount -t ext4 /dev/disk/by-uuid/YOUR-PARTITION-UUID /share