The year was 2001, the tech world was reeling from the effects of the ongoing dot-com bust, Microsoft had recently been deemed a monopoly under US antitrust law, and Intel had just introduced the Pentium 4 to the market. In the midst of the various tribulations of the time came the release of Linux kernel 2.4 on 4 January 2001.
It contained such revolutionary (for the time) features as support for USB, and ISA ‘Plug and Play’ – doing away with the need to configure hardware jumpers or run the special isapnp commands to make various adaptor cards work. Many other features we take for granted today soon followed, including support for logical volumes (LVM) from Sistina (later acquired by Red Hat), software RAID and the ext3 file system.
Kernel 2.4 was revolutionary because it was the first kernel release that was truly embraced by enterprise users for use in their operations. Linux had had support for SMP (symmetric multiprocessing – another term for multiple CPUs) since 2.0, but the improvements in 2.4 driven by the newly involved big players (such as IBM) brought improved scalability, stability and new features that finally pushed it over the edge as a serious contender to proprietary UNIX systems of old.
This was also the first release that saw serious use in embedded computing devices, such as the Sharp Zaurus and the Linksys (now part of Cisco) WRT54G 802.11g wireless router/gateway. I myself worked on control systems for various industrial magnets using 2.4 and remember kernel 2.4.23 with some particular fondness I’ll never forget.
The first 2.4 kernels were a mixed bag. Various necessary but not entirely complete churn in the virtual memory (VM) subsystem throughout the 2.3 ‘development’ kernel series left the early 2.4 kernels somewhat wonky to the point that I can recall certain distribution releases using Alan Cox’s special 2.4.9-ac kernel series, which replaced the stock VM enhancements from Andrea Arcangeli (that weren’t quite ready for prime time) with Rik van Riel’s modifications that made it suitable enough for real-world use.
Those kinks would ultimately get worked out and 2.4 became a very stable kernel on which to base a number of popular software products, as well as many gadgets and gizmos. In fact, 2.4 was so popular that it is still being maintained nearly a decade later, although its original 18-year-old maintainer (Marcelo Tosatti) has long since moved on to other things.
Official 2.4 series maintainer Willy Tarreau has continued to post occasional updates, all the way to 126.96.36.199, which is current as of this writing.
Updates don’t happen all that often now, and in the months since the previous release Willy has seen fewer and fewer remaining 2.4 systems in production, while his employer is apparently ready to kill off the last remaining 2.4-based product (a network load balancer – itself a testament to the longevity of the 2.4 kernel).
So Willy is finally giving notice that the End Of Life is approaching. There will be no more updates if nothing serious happens before one year from now, with the timeline being extended slightly if circumstances require a final 188.8.131.52. Farewell 2.4, you’ve been a good friend to many of us over the years.