boots to userland and runs busybox init

README.md

@@ -8,12 +8,34 @@ Līminis + Nix
 
 ## What is this?
 
-This is a reboot/restart of NixWRT: a Nix-based collection of software
-tailored for domestic wifi router or IoT device devices, of the kind
-that OpenWrt or DD-WRT or Gargoyle or Tomato run on.
+This is a Nix-based collection of software tailored for domestic wifi
+router or IoT device devices, of the kind that OpenWrt or DD-WRT or
+Gargoyle or Tomato run on. It's a reboot/restart/rewrite of NixWRT.
 
 This is not NixOS-on-your-router: it's aimed at devices that are
-underpowered for the full NixOS experience.
+underpowered for the full NixOS experience. It uses busybox tools,
+musl instead of GNU libc, and s6-rc instead of systemd.
+
+
+## Building
+
+These instructions assume you have nixpkgs checked out in a peer
+directory of this one.
+
+You need a `configuration.nix` file pointed to by `<liminix-config>`, a
+hardware device definition as argument `device`, and to choose an
+appropriate output attribute depending on what your device is and how
+you plan to install onto it. For example:
+
+    NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build -I liminix-config=./tests/smoke/configuration.nix --arg device "import ./devices/qemu.nix" -A outputs.default
+
+`outputs.default` is intended to do something appropriate for the
+device, whatever that is. For the qemu device, it creates a directory
+containing a squashfs root image and a kernel, with which you could
+then run
+
+    ./run-qemu.sh result/vmlinux result/squashfs
+
 
 ## Running tests
 
@@ -22,7 +44,6 @@ Assuming you have nixpkgs checked out in a peer directory of this one,
     NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH ./run-tests.sh
 
 
-
 ## Articles of interest
 
 * [Build Safety of Software in 28 Popular Home Routers](https://cyber-itl.org/assets/papers/2018/build_safety_of_software_in_28_popular_home_routers.pdf):