muLinux: A Brief Introduction

muLinux is a miniature, but nearly full-featured distribution (i.e., version) of Linux that can fit on a single floppy disk and can turn almost any personal computer into a temporary but powerful Linux machine in a matter of minutes. Although there are several other single-floppy Linux distributions, none can match muLinux's extensive and unique combination of useful features.

muLinux operates entirely from its floppy disk and from the computer's memory. There is nothing that needs to be installed on a hard disk drive (HDD), although muLinux can be installed if desired. muLinux can be used on any personal computer which has a floppy disk drive and an Intel-compatible (i.e., x86) processor, which is most personal computers other than the Macintosh.

muLinux is well suited for several important types of applications including (1) education, (2) system repair, (3) utilizing old hardware, (4) forensic analysis and (5) proselytizing. For example, some system administrators and consultants use it for system recovery, demonstrations and hardware configuration. Among the many things they appreciate about it is the fact that it can be carried around in a shirt pocket.

muLinux is also an excellent way to improve the utilization of old computer hardware that might otherwise be discarded. For example, it can make an ancient 33MHz 486 with 8MB of RAM (random access memory) and a 40MB HDD into a fully functional workstation suitable for text processing, e-mail and various other applications. It can also be used on diskless (i.e., no HDD) computers, including diskless workstations and computers whose hard disk has died or been removed.

Some educational institutions prefer muLinux for Linux training. One reason is that it allows the use of existing computers which contain only Microsoft Windows on them and on which schools might not want to permanently install Linux. Another is that it is a very economical solution because it can run on computers that might be obsolete for other uses and on very low cost diskless computers.

Among the many features of muLinux are:

(1) The ability to use or install Linux on computers that do not have CD-ROM drives and on computers whose CD-ROM drives have been disabled for security or other reasons; all that is necessary is that they have a floppy drive.

(2) The ability to run completely from the floppy and RAM. This means that muLinux does not have to be installed on a hard disk, with the consequent need to partition (i.e., divide into logically independent sections) the HDD (which can be very difficult and risky for inexperienced users). The ability to run from RAM can also be extremely useful for forensic and repair applications, and it can make it possible to utilize computers that do not have hard disks. muLinux can boot (i.e., start) from its floppy on a computer with a RAM as small as 8MB.

(3) The ability to be installed on a HDD if desired. In fact, installation is fairly simple, and muLinux can be placed in a directory on an existing MS-DOS, Microsoft Windows 9x or Linux partition (i.e., without any need for repartitioning). The advantages of installing on a HDD include higher speed and the ability to run on a computer having as little as 4MB of RAM.

(4) The use of the ext2 Linux native filesystem. This contrasts with some other single-floppy versions of Linux, which use the less advanced minix filesystem. The advantages of ext2 include higher speed, additional timestamps and provision for longer file names.

(5) A very large number of standard Linux commands in the standard directories despite its small size: i.e., more than 100 in /bin, 3 in /sbin, more than 150 in /usr/bin and 13 in /usr/sbin.

(6) The ability to save user configuration data on the floppy for subsequent use.

(7) The ability to connect to the Internet and allow access to the normal network services, including e-mail, news, ftp and http. There are also a number of networking tools, including traceroute, ping, telnet, rlogin, sniffit, nmap and tcpdump. The disk can even be used to run telnet or ftp services.

(8) The availability of downloads for making twelve additional floppies with optional add-on functions. One of these contains the X Window System, the standard system for managing GUIs (graphical user interfaces) on Unix-like operating systems, and a number of applications that run on it. Others include Samba (Microsoft Windows network server), a Netscape browser, the GCC (GNU Compiler Collection), a Java Virtual Machine, the Perl and Tcl/Tk programming languages, and the TeX typesetting system.

(9) Free software, i.e., available to everyone at no cost and free to use for any purpose, including to copy, modify and give away or sell.

muLinux has some disadvantages as well, and these are largely a result of its ability to fit on a single floppy disk. For example, in contrast to most Unix-like operating systems, it is a single user system. This means that the user has full root (i.e., administrative) privileges, and thus the usual security of Unix-like systems is lacking. For this reason, although it has good networking capabilities, muLinux is not well suited for use as a high performance system with multiple users.

muLinux was developed by Michele Andreoli, an Italian professor of mathematics and physics and a consultant for embedded Linux projects. He named it after the Greek letter mu (which is used to indicate the millionth part of something) because of its very small size.

In contrast to many other Linux distributions, the emphasis of muLinux is not on using the most recent software components. For example, some of the components are as old as 1998, including a 2.0.x kernel and some bash scripts. Andreoli points out that neophytes should thus avoid the use of muLinux to evaluate Linux or open source software in general.

As of early June, 2005, the most recent version was 14r0, which was released in February 2004. muLinux itself is not currently under active development, according to Andreoli.

It is often said these days that the floppy disk is obsolete and should be abolished. Well, perhaps it will be obsolete some day, but not quite yet.

muLinux's home page is

Created June 20, 2004. Updated June 19, 2005.
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