Converting EXT3 partition into EXT4 on Ubuntu

EXT4 type partition is the successor of EXT3, but it may not be turned on by default installation. Indeed, EXT4 driver is backward compatible with EXT3/EXT2 partition. The conversion from EXT3 to EXT4 partition is straight forward.

Please backup important data and software you have been using on Ubuntu Linux.

BEFORE DOING ANYTHING, PLEASE SHUTDOWN ALL LAMPP RELATED PROCESSES:

$ sudo /opt/lampp/lampp stop

To switch the existing Ext3 file system to the new Ext4 driver, it is necessary to edit a configuration called "fstab":

$ sudo nano /etc/fstab

Look for ext3 on the line that defines your disk and change it to ext4.

To ensure the right device to be converted, you may check the name of the device by issuing the following command:

$ df -h

Make a note of the device as you will need it in the next step. In the example above, the device for the encrypted partition is "/dev/mapper/encrypted".

Next reboot your system. This is required so that you switch to the Ext4 Kernel driver. Do not continue without rebooting first.

Enable Ext4 features:

$ sudo tune2fs -O extents,uninit_bg,dir_index /dev/mapper/encrypted

WARNING: Once you run this command, the filesystem will no longer be mountable using the ext3 filesystem!

After running this command (specifically, after setting the uninit_bg parameter), it is also important to run fsck to fix up some on-disk structures that tune2fs has modified:

$ e2fsck -yfDC0 /dev/mapper/encrypted

Notes:

Running fsck will complain about "One or more block group descriptor checksums are invalid" - this is expected and one of the reasons why tune2fs requests to fsck.
By enabling the extents feature new files will be created in extents format, but this will not convert existing files to use extents. Non-extent files can be transparently read and written by Ext4.
If you convert your root filesystem ("/") to ext4, and you use the GRUB boot loader, you will need to install a version of GRUB which understands ext4. Your system may boot OK the first time, but when your kernel is upgraded, it will become unbootable (press Alt+F+F to check the filesystem).
If you do the conversion for the root fs on a live system you'll have to reboot for fsck to run safely. You might also need to add rootfstype=ext4 to the kernel's command line so the partition is not mounted as ext3.

WARNING:
It is NOT recommended to resize the inodes using resize2fs with e2fsprogs 1.41.0 or later, as this is known to corrupt some filesystems.
If you omit "uninit_bg" on the tunefs command, you can skip the fsck step.