Create a virtual block device
Linux supports a special block device called the loop device, which maps a normal file onto a virtual block device. This allows for the file to be used as a "virtual file system".
Create a file of size 1G:
fallocate -l 1G disk.img
du -hs disk.img
Create a loop device with this file:
sudo losetup -f disk.img
-ffinds an unused loop device.
Find the name of the loop device that was created: