Q:

What is dd if=/dev/zero of=/EMPTY bs=1M

Often times I see this command for use when creating a Vagrant box
sudo dd if=/dev/zero of=/EMPTY bs=1M

To me it seams that it is copying a lot of NULL characters into a file named EMPTY at the FS root 1MB at a time. My question is how does doing this optimize the space usage on the disk once the file is removed.

A:

It effectively writes zeroes to all empty space on the volume; this allows for better compression of the physical file containing the virtual disk.

