You can take a disk file, format it as an ext2, ext3, or reiser filesystem, and then mount it, just like a physical drive. It’s then possible to read and write files to this newly-mounted device. You can also copy the complete filesystem, since it is just a file, to another computer. If security is an issue, read on. This article will show you how to encrypt the filesystem and mount it with ACL (Access Control Lists), which gives you rights beyond the traditional read (r), write (w), and execute (x) permissions for the three user groups “file”, “owner”, and “other”.