Immutable Systems: Cross-Compiling for RISC-V using Nix Flakes
In my last post, we built whole disk images for embedded systems using Nix. This approach is well suited for RISC-V or ARM systems, but you probably don’t have a powerful build box for this architecture. You wouldn’t want to build a Linux kernel for hours on a RISC-V single-board computer praying that you don’t run out of RAM…
In this blog post, we will use the same NixOS configuration to cross-compile system images for x86, RISC-V and ARM from our powerful x86 build server.
Let’s go over some theory first and then look at how this applies to our flake from the previous post. A complete example lives in here. For the version that was current when this blog post was written, check out the blog-post-2 tag.
nixpkgs has excellent cross-compilation support. There are also excellent resources for cross-compiling individual packages. Cross-compiling whole systems is even easier, but not as well documented. There are two main ways to configure it. For a deeper discussion, check out this post.
The second approach is to build a cross-compiling pkgs set yourself and then just use this for your NixOS configuration. Assuming nixpkgs is the nixpkgs flake input, you can create it like this:
