DSL-kun is the male personification of the Damn Small Linux operating system, a portable Linux distribution with a sub-50MB footprint. Due to the simplicity, size and relatively-young age of the OS, DSL-kun is personified as a young boy of around 3 or 4 years of age but with a lilliputian height of around 1.25cm (or 0.5 inches). Although his older sister DSL-tan personifies the same OS, she has a significantly taller stature at 15cm or 6 inches, alluding to the fact that the Damn Small Linux logo features a miniature penguin carrying a near-microscopic one. One could also equate DSL-kun as the OS-kun equivalent of the character “Tom Thumb”, a pun on a USB “thumbdrive” which is a common installation medium for the OS.
Aside from his miniature size, DSL-kun is little different in appearance from any other boy his age. He has short, dark-brown hair combed in the same manner as his sister, and tops it with a baby penguin cap that is also in perfect imitation of his sister (right down to wearing it sideways). He wears a dark blue sweater featuring the Fluxbox emblem over a long-sleeved white shirt, as well as blue jeans and grey shoes. The sweater itself will change based on the latest desktop wallpaper – it may bear a green, gutted-out circle referencing the Fluxbox environment in version 3.0, or blue radial streaks referencing the JWM wallpaper in version 4.0.
Though the young, DSL-kun is capable of performing tasks years ahead of his physical age, he still remains inexperienced and naive, and so is highly dependent on his sister's guidance and use of “N” magic (a reference to DSL-N, a version of Damn Small Linux with a greater application range). Though his appearance and innocent childishness can instantly win anyone's love, his tiny size ensures that he remains all but invisible to regular-sized OS-tans. He has friends among other small characters such as Windows CE-tan, PalmOS-tan, the iPod-tans, and the kinder, gentler virus-tans, who at times go as far as to babysit or tutor him. But for the most part he lives alone with his older sister, tucked away inside the comfort and safety of her penguin bag.