The day of the mold-your-own OS has come, and Linux is the clay.
Linux provides free and open access to the source for the OS itself. Developers are free to tailor a custom Linux -- even down to the level of the kernel itself. You can trim away drivers, services, and other OS components unneeded by the task for which the custom distribution will be targeted.
[Check out InfoWorld Test Center's previous roundup of specialized Linux distributions.]
In addition, because Linux thrives on a universe of free software, developers can be choosy about the pre-installed packages they supply with their custom system. One can easily construct a user environment tuned to a specific application.
The specialized Linuxes in this roundup showcase the advantages of customizing both OS components and user-level software. I look at a pair of firewall Linuxes -- IPCop and m0n0wall -- a Linux SAN/NAS appliance called OpenFiler, and two Linuxes for musicians -- Ubuntu Studio and Musix. The final duo of distributions, Ubuntu Christian Edition and Ubuntu Muslim Edition, are targeted at members of those corresponding religions.