WIP archlinux bootstrap from nixos

pkgs/bootstrap/archlinux/default.nix

@@ -0,0 +1,102 @@
+{
+  lib,
+  concatText,
+  fetchzip,
+  stdenvNoCC,
+  writeText,
+  writeShellApplication,
+
+  bash,
+  cacert,
+  coreutils,
+  pacman,
+  systemd,
+  zstd,
+
+  repos ? ["core" "community" "extra"],
+  keyring-version ? "20241015-1",
+  keyring-hash ? "sha256-7IegfprKTNn0aPRMgTw34SEc/GRCfy92mE9CVI4rxr0=",
+  mirror ? "https://mirror.rackspace.com/archlinux/$repo/os/$arch",
+}: rec {
+  keyring = (fetchzip.override { withUnzip = false; }) {
+    url = "${builtins.replaceStrings ["$repo" "$arch"] ["core" "x86_64"] mirror}/archlinux-keyring-${keyring-version}-any.pkg.tar.zst";
+    hash = keyring-hash;
+    nativeBuildInputs = [ zstd ];
+    stripRoot = false;
+    postFetch = ''
+      rm "$out"/.BUILDINFO "$out"/.INSTALL "$out"/.MTREE "$out"/.PKGINFO
+      mkdir "$out"/share/pacman -p
+      mv "$out"/usr/share/pacman/keyrings "$out"/share/pacman
+      rm -rf "$out"/usr
+    '';
+  };
+
+  pacman_conf_in =
+    writeText
+      "pacman-mirrors.conf"
+      (lib.strings.concatLines
+        (lib.map
+          (repo: ''
+            [${repo}]
+            Server = ${mirror}
+          '')
+          repos));
+
+  pacman_conf = concatText "pacman.conf" [ "${pacman}/etc/pacman.conf" pacman_conf_in ];
+
+  bootstrap = writeShellApplication {
+    name = "archlinux-bootstrap";
+
+    runtimeInputs = [ coreutils pacman systemd ];
+
+    text = ''
+      if [ $# -lt 1 ]; then
+        echo "usage: $0 [directory] [pkgs ...]"
+        exit 1
+      fi
+
+      newroot="$1"
+      shift
+
+      echo "Installing arch linux to $newroot"
+
+      # set up new base filesystem
+      install -dm0755 "$newroot"
+      install -dm0755 "$newroot"/var/{cache/pacman/pkg,lib/pacman,log}
+      install -dm0755 "$newroot"/{dev,run,etc/pacman.d}
+      install -dm1777 "$newroot"/tmp
+      install -dm0555 "$newroot"/{sys,proc}
+
+      # set up mountpoint for nix
+      install -dm0755 "$newroot"/nix
+
+      # temporarily set up /etc/mtab, pacman needs this to work
+      ln -sf /proc/mounts "$newroot"/etc/mtab
+
+      # fully initialize the keyring ahead of entering the container
+      pacman_conf="${pacman_conf}"
+      pacman-key --gpgdir "$newroot"/etc/pacman.d/gnupg --config "$pacman_conf" --init
+      pacman-key --gpgdir "$newroot"/etc/pacman.d/gnupg --config "$pacman_conf" \
+        --populate archlinux --populate-from "${keyring}/share/pacman/keyrings"
+
+      # install the config file
+      install -Dm0755 "$pacman_conf" "$newroot"/etc/pacman.conf
+
+      # bootstrap the system. allow pacman to overwrite the existing mtab entry
+      systemd-nspawn -D "$newroot" --bind-ro=/nix \
+        -E SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt \
+        -E PATH=/usr/bin/ \
+        -- \
+        "${pacman}/bin/pacman" -Sy --noconfirm --overwrite /etc/mtab base "$@"
+
+      # remove nix mount point
+      rmdir "$newroot"/nix
+
+      echo "Done installing!"
+      echo "Set root password:"
+      echo "  sudo systemd-nspawn -UD \"$newroot\" -- /bin/passwd root"
+      echo "Boot system:"
+      echo "  sudo systemd-nspawn -bUD \"$newroot\""
+    '';
+  };
+}