Halleluja! The Second Coming of Windows Subsystem For Linux blesses Insider faithful

OMG, emoji panel also fixed in Microsoft's 2020 OS


Microsoft has given its army of unpaid testers some Linux loving with the latest build of next year's Windows 10.

Build 18917 arrived overnight with improvements to the narrator and options to stop the thing "optimising" the life out of a user's bandwidth during delivery.

However, Windows Subsystem for Linux (WSL) 2 is the highlight of the release.

WSL 2 does what would be unthinkable a few short years ago and drops a Linux kernel into the Windows OS – a tweaked version of 4.19 to be precise. The result is something that enjoys full system call compatibility, according to Microsoft, and considerably snappier file performance inside Linux. It also happily runs ELF64 binaries.

Windows Terminal

The Year Of Linux On The Desktop – at last! Windows Subsystem for Linux 2 brings the Linux kernel into Windows


WSL 2 is aimed at encouraging developers to stick with the Windows 10 platform and users familiar with its predecessor will not find things particularly jarring. As promised by the gang during Microsoft's recent developer shindig Build, converting existing distros to run on version 2 is a simple wsl --set-version [Distro] 2 from PowerShell and away you go.

A similar command will set WSL 2 as a default, but we wouldn't recommend doing that right now – things are a little flaky.

Getting WSL 2 up and running requires some more PowerShell action to enable the Virtual Machine Platform followed by a restart.

Microsoft claims a 20x improvement on unpacking a zipped tarball and between 2-5x faster when doing a git clone or cmake. While we didn't see figures that were quite that dramatic, things are certainly a lot perkier than version 1 and, of course, the worry that one might do something to make the abstraction layer a bit sad is now absent.

It's all very solid and stable considering this is very much preview code.

However, there are issues – some by design and some because, well, this isn't quite ready for production just yet.

First up is networking. The IP address of the distro and the Windows host differs, and a simple LocalHost does not work, which is a pain. The team has acknowledged the problem and described it as "very high on our priority list to fix".

Then there is the memory – there is no getting away from the fact that Microsoft's new shiny is, at its heart, a jumped-up virtual machine. It may be "lightweight" but is still going to grab some RAM.

The VM issue also rears its head with the file system, which is now a VHD using the ext4 file system and configured with an initial size of 256GB. If your distro needs to go big, you will have to dive into the command line to grow things. And that change in architecture has also introduced a noticeable slowdown in shunting files between operating systems compared to WSL 1.

The creators of Pengwin, a distro tweaked specifically to run well with WSL 1, succinctly described WSL 2 as "super fast", but with "limitations".

The other notable change in the new Windows 10 build is the arrival of an option to throttle the bandwidth consumed by the OS as part of what Microsoft refers to as "delivery optimisation" and what consumers might describe as "why is my internet suddenly so slow?"

Rather than choose a percentage of usage, which the Windows team admits "isn't providing enough relief", users can now set absolute limits for foreground and background data usage.

Otherwise it is very much business as usual – some games with anti-cheat code will still crash and Realtek SD card readers might not work. However, the gang has dealt with the pesky problem of the preview OS burning through RAM and falling over during download and also the delightfully retro lag when dragging around the emoji panel.

Thank goodness for that.

Build 18917 is also known as 20H1, and is due to hit end users in 2020. Of the next Windows 10 release, due in the back-end of 2019 and referred to as 19H2, there remains no sign. ®

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