What better way to kickstart a brand new month than with a brand new Linux kernel.

Yes, Linux 5.15 is now officially released.

Announcing the new kernel’s arrival on the Linux Kernel mailing list Linux founder Linus Trovalds writes:

“The last week of 5.15 was mainly networking and gpu fixes, with some random sprinkling of other things (a few btrfs reverts, some kvm updates, minor other fixes here and there – a few architecture fixes, couple of tracing, small driver fixes etc)”, adding that “…on the whole 5.15 was fair small and calm (sic)”.

So what’s new?

Linux Kernel 5.15 Features

Latest kernel supports all this and more

As you’d expect, Linux 5.15 includes an impressive itinerary of improvements. These range from small fixes at lower levers through to major restructuring of core functionality. The following roundup highlights the additions that caught my interest/eye but is by no means an exhaustive run-through.

The headline change in Linux 5.15 the inclusion of a new NTFS file system driver, ‘NTFS3’. If you read or write to an NTFS partition in Linux (in distros like Ubuntu) it’s probably been using the older user-space ntfs-3g driver. In Linux 5.15 the kernel gains a new and hugely improved NTFS implementation thanks to code from Paragon Software.

Also new is ksmbd — a new in-kernel SMB file server. This is not intended to replace Samba by compliment it by providing a lightweight and fast kernel-space module offering server-side SMB3 with ‘better lease handling’ that’s compatible with user-space tools and libraries.

After 17 years of development realtime preemption locking code has been merged; and DRAM memory pages are now moved to persistent memory instead of being discarded.

The effort to get Linux working on Apple Silicon continues to bear fruit. Amongst many smaller changes is a new Apple M1 IOMMU driver. While Linux on M1 isn’t quite “end-user ready” yet the pace of progress is fast. Expect further leaps forward in this area by the time Linux 5.16 rolls out.

Linux 5.15 includes high resolution scrolling for the Apple Magic Mouse; a newer Realtek RTL8188EU Wi-Fi driver; a driver that allows access to OTP read-only memory on the Wii U — *1UP SFX* — and support for power profiles on select Acer laptops.

Among a swathe of single-board computer additions is mainline kernel support for the NVIDIA Jetson TX2 NX developer kit.

Further Intel Alder Lake support is included, while groundwork is laid for AMD Cyan Skillfish and Intel XeHP and DG2/Alchemist graphics. There’s also a new AMD Van Gogh APU audio driver which will benefit the upcoming Steam Deck.

Among numerous file system improvements is a set of fresh enhancements to EXT4 (Ubuntu’s default file system) including better delalloc buffer write performance; EROFS filesystems now support direct I/O on uncompressed files; and Btrfs picks up support for fs-verity file integrity assurance to allow the kernel to detect any modifications made to individual read-only files.

For more details on this kernel release check out the LWN merge reports here and here, read over Phoronix’s roundup, or pour over the comprehensive change-set on the Kernel Newbies wiki.

Getting Linux 5.15

Linux 5.15 is available to download as a source code from the kernel.org website — but you’ll need to compile this by hand to get it working on your preferred Linux distro.

On rolling release distros like Arch the new kernel will be packaged and made available sooner than it will on snapshot releases like Ubuntu, Linux Mint, and Zorin OS.

That said, the Ubuntu kernel team do make mainline builds of 5.15 available for Ubuntu but — and it’s a 128px size but — mainline builds are not recommended for regular users, just developers! Use them at your own risk, people!

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