February 2021 round-up

This started off the work from @eamsden, where uses of <nixpkgs> were removed almost everywhere in #238.

With the changes, the value <nixpkgs> is now used only at one location, at the start of the evaluation, in a way that can be overridden easily if needed.

This means that evaluation now works fine without a NIX_PATH. This is useful to allow users of Nix flakes to use the project.

Similar changes were made in #310 to rely on a single <nixpkgs> value for release.nix and example configuration evaluations.

When #262 was merged in December, it was done so with two main features missing.

Time was taken to finish the boot features for stage-0 in #300.

When a device supports stage-0 boot, a new toggle is shown in the generations list allowing the user to skip rebooting into the generation’s kernel.

When booting a generation, the device tree built from the same kernel source tree is now used. The pull request itself contains technical details. This was less trivial than expected.

Using armv7 with Nixpkgs or NixOS is not always easy. There is no binary cache, and cross-compilation is as YMMV as it is for AArch64.

This is the reason why armv7 Mobile NixOS devices haven’t seen much work done and things slowly started not working.

With #306 time was taken to ensure contributors with armv7 devices wouldn’t be left with hard to debug issues from Mobile NixOS itself.

With this work finally taken care of, there is a recent known good starting point to use for armv7 devices.

A few recent WIP device ports were made on top of these changes. Stay tuned as they may become supported devices at some point in the future.

With #320, Android flashable zip support was added to Mobile NixOS. This is used to produce .zip files that can be installed to the devices using the mechanism commonly used to apply OTA updates in Android.

Why would this new flashing method be needed or desired?

First, it is more universal than fastboot, as some OEMs implement alternative flashing modes in their devices (e.g. Odin for Samsung).

Then, some devices (e.g. oneplus-oneplus3) have problematic fastboot flash behaviours when flashing to the userdata partition. Some devices (e.g. amazon-austin) need to apply some out-of-band "fixes" to the boot images, which happens for free when using a flashable zip.

With that said, all methods to flash the system to the device should produce the same outcome in most cases. As long as your device boots fine, there is no reason to prefer one or the other flashing method.