I am using Linux as guest OS in VirtualBox. I deleted huge number of files from its filesystem. Now i want to shrink the filesystem image file (vdi). The shrinking works by compressing filesystem image wherever it has "null" value in disk.
It seems an application called zerofree can write "null" into free space of filesystem in such a way that it becomes sparse. But the instructions say it works only on ext2/ext3. I have ext4 on my guest OS.
Why won't it work on ext 4 (reason cited is "extents", but can someone shed more light on it) ?
Will it work, If i mount the ext 4 as ext 3 and then remount as ext 4 ?
Any other tools that can do similiar thing as zerofree on ext ?