Linus Torvalds, initiator of the Linux kernel that drives the GNU/Linux operating system, said in an email this week that Linux is still rapidly evolving 10 years after its creation, although this can lead to difficulties in managing kernel development.
Torvalds made his comments about the release of the 2.4.x kernel, the current "stable" branch of the kernel designed for use in finished products. Such stable, production kernels are designated by an even number after the first decimal point. When a development kernel, like 2.3.x, reaches stability, it is released as a stable kernel -- for instance 2.4 -- but it can be difficult to know when to make the transition. Development kernels such as 2.3 and 2.5 are experimental and are intended only for programmers.
Far more people use a stable kernel like 2.4 than a development kernel, so they are statistically more likely to discover errors, Torvalds said. "The people you really want to test it won't test it until it is stable, and you cannot make it stable before you have lots of testers," he wrote in the message, later posted on open source site NewsForge. "A basic chicken-and-egg problem, in short."
With Linux, things can be more difficult because of the OS's dynamism. "The real solution is to make fewer fundamental changes between stable kernels, and that's a real solution that I expect to become more and more realistic as the kernel stabilises," Torvalds wrote. "But you also have to realise that 'fewer fundamental changes' is a mark of a system that isn't evolving as quickly, and that is reaching middle age. We are probably not quite there yet."
The 2.5 development kernel, initiated last week, branches off from the stable 2.4.15 version, which has given it "a good start", Torvalds said. "The system does look fairly stable, with just some silly problems that have known solutions and aren't a major pain to handle," he wrote.
In related news, kernel 2.4.15 was replaced by 2.5.16 on Monday because of a bug that could corrupt file systems. The file-system corruption bug had earlier cropped up in pre-release version 9 of kernel 2.4.15.
Stable kernels generally go through an additional period of testing by Linux distribution companies before they are included in a finished operating system. For example, Red Hat's latest operating system release, 7.2, uses the 2.4.7 kernel.
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