Devil-Linux is a distribution which boots and runs completely from CDROM. The configuration can be saved to a floppy diskette or a USB pen drive. Devil Linux was originally intended to be a dedicated firewall/router but now Devil-Linux can also be used as a server for many applications. Attaching an optional hard drive is easy, and many network services are included in the distribution.
The system is designed to install without the use of a hard drive. It requires the use of a CDROM and a write-protected floppy. The CDROM provides the operating system, and the floppy provides the configuration information, via a tarball that is unpacked into the /etc directory. In this way, the system is fully configurable, yet the running system has no writeable device.