install.sh: add ability to install non-native architecture

The result is that it now requires to be run only on NixOS but that
should be fine.

3 files changed, 83 insertions, 32 deletions

diff --git a/common.sh b/common.sh
index 9b6f48c..d3ddbc3 100644
--- a/common.sh
+++ b/common.sh
@@ -80,6 +80,10 @@ device_system() {
 	nix eval --raw ".#nixosConfigurations.$1.config.nixpkgs.system"
 }
 
+build_system() {
+	nix eval --raw --impure --expr 'builtins.currentSystem'
+}
+
 # Validates if link is valid.
 build_validate() {
 	local device="$1"
@@ -93,12 +97,10 @@ build() {
 	local device="$1"
 	shift
 
-	local toplevel=".config.system.build.toplevel"
-	if [ "$(device_system "$device")" = "armv7l-linux" ]; then
-		toplevel=".config.system.build.cross.x86_64-linux${toplevel}"
-	fi
-	if [ "$(device_system "$device")" = "aarch64-linux" ]; then
-		toplevel=".config.system.build.cross.x86_64-linux${toplevel}"
+	local toplevel="config.system.build.toplevel"
+	local bsystem="$(build_system)"
+	if [ "$bsystem" != "$(device_system "$device")" ]; then
+		toplevel="config.system.build.cross.$bsystem.$toplevel"
 	fi
 
 	stage "Building system for device: $device"
@@ -106,7 +108,7 @@ build() {
 		-o "$(result "${device}")" \
 		--keep-going \
 		"$@" \
-		"${0%/*}#nixosConfigurations.${device}${toplevel}"
+		"${0%/*}#nixosConfigurations.${device}.${toplevel}"
 }
 
 ## Copy NixOS system ###########################################################
diff --git a/install.sh b/install.sh
index a0ec3b7..823a9f5 100755
--- a/install.sh
+++ b/install.sh
@@ -1,37 +1,68 @@
 #!/bin/sh
 set -eu
-hostname="${1:-$(hostname)}"
-root="${2:-}"
-
-_sudo() {
-	if [ "$(id -u)" -ne 0 ]; then
-		"$@"
-	else
-		sudo -p 'Sudo password: ' -- "$@"
-	fi
-}
-
-if [ "$hostname" = "nixos" ]; then
-	echo "The hostname is the default one, that is not right for sure." >&2
-	echo "Please specify the correct hostname as the first argument!" >&2
+hostname="$1"
+root="${2:-$(pwd)}"
+src="$(readlink -f "${0%/*}")"
+
+if [ "$(id -u)" -ne 0 ]; then
+	echo "Run this as root!" >&2
 	exit 1
 fi
 
+if ! command -v git >/dev/null; then
+	exec nix shell 'nixpkgs#git' -c "$0" "$@"
+fi
+
 if [ ! -s "$root/.personal-secrets.key" ]; then
 	echo "Please paste the personal secret key (terminate using ^D)" >&2
 	sudo tee "$root/.personal-secrets.key" >/dev/null
 fi
 
-eval "$(ssh-agent)"
-echo "Please paste the SSH access key now (terminate using ^D):" >&2
-ssh-add -
-trap 'kill "$SSH_AGENT_PID"' EXIT
+if [ -f "$src/flake.nix" ]; then
+	flake="$src"
+else
+	flake="git+https://git.cynerd.cz/nixos-personal"
+	eval "$(ssh-agent)"
+	echo "Please paste the SSH access key now (terminate using ^D):" >&2
+	ssh-add -
+	trap 'kill "$SSH_AGENT_PID"' EXIT
+fi
+
+buildSystem="$(nix eval --raw --impure --expr 'builtins.currentSystem')"
+targetSystem="$(nix eval --raw "$flake#nixosConfigurations.$hostname.pkgs.system")"
 
-flake="git+https://git.cynerd.cz/nixos-personal#$hostname"
-if [ -z "$root" ]; then
-	nix shell nixpkgs\#git --command \
-		"_sudo \"\$(command -v nixos-rebuild)\" switch --flake '$flake' --fast"
+toplevel="config.system.build.toplevel"
+if [ "$buildSystem" != "$targetSystem" ]; then
+	toplevel="config.system.build.cross.$buildSystem.$toplevel"
+fi
+
+if [ -f "$src/flake.nix" ]; then
+	# Build in system when running from sources
+	result="$(nix build --no-link --print-out-paths \
+		"$flake#nixosConfigurations.$hostname.$toplevel")"
+	nix copy --to "$root" "$result" 
 else
-	nix shell nixpkgs\#git nixpkgs\#nixos-install-tools --command \
-		"_sudo \"\$(command -v nixos-install)\" --flake '$flake' --root '$root'"
+	result="$(nix build --no-link --print-out-paths \
+		"$flake#nixosConfigurations.$hostname.$toplevel" \
+		--store "$root" --extra-substituters 'auto?trusted=1')"
+fi
+
+nix-env --store "$root" --extra-substituters 'auto?trusted=1' \
+	-p "$root/nix/var/nix/profiles/system" --set "$result"
+
+# Mark the target as a NixOS installation, otherwise switch-to-configuration will chicken out.
+mkdir -m 0755 -p "$root/etc"
+touch "$root/etc/NIXOS"
+
+# Copy over binfmt runners if required
+if [ "$buildSystem" != "$targetSystem" ]; then
+	mkdir -p "$root/run/binfmt"
+	for binfmt in /run/binfmt/*; do
+		nix copy --to "$root" "$(readlink -f "$binfmt")" 
+		ln -sf "$(readlink -f "$binfmt")" "$root/$binfmt"
+	done
 fi
+
+ln -sfn /proc/mounts "$root/etc/mtab" # Grub needs an mtab.
+NIXOS_INSTALL_BOOTLOADER=1 nixos-enter --root "$root" -- \
+	/nix/var/nix/profiles/system/bin/switch-to-configuration boot
diff --git a/nixos/modules/compile.nix b/nixos/modules/compile.nix
index 6c42951..ffa339f 100644
--- a/nixos/modules/compile.nix
+++ b/nixos/modules/compile.nix
@@ -17,7 +17,25 @@ with lib;
       max-jobs = 32;
       cores = 0;
     };
-    boot.binfmt.emulatedSystems = [ "armv7l-linux" "aarch64-linux" ];
+    boot.binfmt.registrations = {
+      aarch64-linux = {
+        fixBinary = true;
+        wrapInterpreterInShell = false;
+        interpreter = (lib.systems.elaborate { system = "aarch64-linux"; }).emulator pkgs;
+        magicOrExtension = "\\x7fELF\\x02\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\x00\\xb7\\x00";
+        mask = "\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xfe\\xff\\xff\\xff";
+      };
+      armv7l-linux = {
+        fixBinary = true;
+        wrapInterpreterInShell = false;
+        interpreter = (lib.systems.elaborate { system = "armv7l-linux"; }).emulator pkgs;
+        magicOrExtension = "\\x7fELF\\x01\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\x00\\x28\\x00";
+        mask = "\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xfe\\xff\\xff\\xff";
+      };
+    };
+    nix.settings.extra-platforms = [
+      "aarch64-linux" "armv7l-linux"
+    ];
 
     environment.systemPackages = with pkgs; [
       # Tools