2015 - A Big Year 4 Linux
2015 was another banner year for the Linux kernel, with a robust slate of mainline kernel developments and new 'big' number release.
On the Linux kernel front, there were five big mainline releases, including a move to new 'big' number. The first Linux kernel release of 2015 was also the last of the Linux 3.x series. Linux 3.19 was released on February 9, and includes a news lockless page counter for improving memory handling.
Linus Torvalds had been hinting that when the numbers got too big in the 3.x series he was going to push the number to 4.0 and that's what happened for Linux 3.20 which was renumbered as Linux 4. The Linux 4.0 kernel was officially released on April 12, marking the first major number change since the Linux 3.0 number rollover in 2011.
With Linux 4.0 the big new addition is the introduction of Live kernel patching, which Torvalds actually downplayed in his release announcement.
"Feature-wise, 4.0 doesn't have all that much special," Torvalds wrote in his Linux 4.0 release message. "Much has been made of the new kernel patching infrastructure, but realistically, that not only wasn't the reason for the version number change, we've had much bigger changes in other versions."
Another item that landed during the Linux 4.0 kernel release cycle was a new Linux code of conduct that stipulates:
"Try to keep in mind the immortal words of Bill and Ted, 'Be excellent to each other."
Following Linux 4.0 there were three additional kernel releases in 2015:
Linux 4.1 debuted on June 21, adding the TraceFS filesystem to Linux.
Linux 4.2 was released at the end of August after 8 release candidates. Linux 4.2 provides a number of security focusses enhancements including support for Linux security module stacking and the Jitter Entropy Random Number Generator.
The Linux 4.3 kernel was the final kernel release of 2015 and it was officially released on November 1 after seven release candidates. The most noteworthy item in the 4.3 release is the removal of the EXT3 filesystem, which had long been the default.
Sean Michael Kerner is a senior editor at LinuxPlanet and InternetNews.com. Follow him on Twitter @TechJournalist