Technically Linux is just an operating system kernel and only the first stage in making a useful system. Many other programs, libraries and configuration files need adding to a basic kernel before a usable system can be created. When the Linux kernel was first developed most of these extra components already existed.
The GNU project, started by Richard Stallman, intended to create a free (both in the free, as in free beer sense and free, as in liberty sense) Unix compatible system. The GNU project started building a set of tools and utilities with the intention of creating kernel as its final stage (the project, called Hurd does exist but is still in an immature state). The Linux kernel was combined with the GNU utilities to create a viable system (often called GNU/Linux).
Starting from scratch and combining a kernel with all the required utilities and adding a set of application programs to create a computer system that can be used for real work is not a trivial task. Fortunately several organisations some commercial and some volunteer offer ready made kits called distributions. Well known distributions include Red Hat, Fedora, SUSE, Debian, Mandrake, Red Flag and many others. Each distribution tends to address slightly different requirements. Red Hat, SUSE and Mandrake are all commercial distributions they tend to emphasise ease of install and use over performance. These distributions make good desktop and server environments but are perhaps a little fat for an embedded platform. Other distributions emphasise embedded real-time performance.
The Heber Axis device driver should build on most modern desktop distributions. The Heber Axis device driver needs a modern version of GCC (the GNU compiler) and a set of configured kernel sources matching the kernel it will finally be used with.
For the demonstration system, which runs off Compact Flash, a much thinner distribution is required. The emphasis is on reducing the system's foot print so it fits on Compact Flash. Heber Ltd. have chosen to use a Debian based system to address this requirement. Debian is a volunteer supported distribution with a good reputation and which offers great control over its installation. Debian is not the only choice, Gentoo is another, and it is possible to build a custom distribution from scratch.
For further information see the Linux from Scratch Website.
Because the interface between the kernel and user applications is well defined and stable, the user is not forced to use the distributions kernel. Subject to making the correct modifications to the boot loader data it is straightforward to replace one kernel with another.