turning an "ext2" or "ext3" file system into an "ext4" one

• en.wikipedia.org/wiki/Ext4
• ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4

root# tune2fs -j /dev/sdXY # add an ext3 journal, if we start with ext2
root# tune2fs -O extents,uninit_bg,dir_index /dev/sdXY
root# e2fsck  -f /dev/sdXY # maybe you want to add …
                           # "-C 0" : progress bar
                           # "-p"   : automatically repair!
                           # "-D"   : optimize directories

To be worked on …