diff --git a/boot-tar.go b/boot-tar.go
new file mode 100644
index 0000000..16e5b05
--- /dev/null
+++ b/boot-tar.go
@@ -0,0 +1,176 @@
+package main
+
+import (
+	"archive/tar"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+func rmTempFile(f *os.File) {
+	f.Close()
+	if err := os.Remove(f.Name()); err != nil {
+		log.Print("failed to remove ", f.Name(), ": ", err)
+	}
+}
+
+func buildBootTar(out io.Writer, ctx *renderContext) (err error) {
+	grubCfg, err := ioutil.TempFile(os.TempDir(), "grub.cfg-")
+	if err != nil {
+		return
+	}
+	defer rmTempFile(grubCfg)
+
+	_, err = grubCfg.WriteString(`
+search --no-floppy --set=root --part-label boot
+
+insmod all_video
+set timeout=3
+
+set bootdev=PARTNAME=boot
+
+menuentry "Direktil" {
+    linux  /current/vmlinuz direktil.boot=$bootdev
+    initrd /current/initrd
+}
+`)
+	if err != nil {
+		return
+	}
+	grubCfg.Close()
+
+	// FIXME including in grub memdisk for now...
+	kernelPath, err := ctx.distFetch("kernels", ctx.Group.Kernel)
+	initrdPath, err := ctx.distFetch("initrd", ctx.Group.Initrd)
+
+	grubMk := func(format string) ([]byte, error) {
+		grubOut, err := ioutil.TempFile(os.TempDir(), "grub.img-")
+		if err != nil {
+			return nil, err
+		}
+		defer rmTempFile(grubOut)
+		if err := grubOut.Close(); err != nil {
+			return nil, err
+		}
+
+		cmd := exec.Command("grub-mkstandalone",
+			"--format="+format,
+			"--output="+grubOut.Name(),
+			"boot/grub/grub.cfg="+grubCfg.Name(),
+			"current/vmlinuz="+kernelPath,
+			"current/initrd="+initrdPath,
+		)
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		if err := cmd.Run(); err != nil {
+			return nil, err
+		}
+		return ioutil.ReadFile(grubOut.Name())
+	}
+
+	arch := tar.NewWriter(out)
+	defer arch.Close()
+
+	archAdd := func(path string, ba []byte) (err error) {
+		err = arch.WriteHeader(&tar.Header{Name: path, Size: int64(len(ba))})
+		if err != nil {
+			return
+		}
+		_, err = arch.Write(ba)
+		return
+	}
+
+	ba, err := grubMk("x86_64-efi")
+	if err != nil {
+		return err
+	}
+
+	err = archAdd("EFI/boot/bootx64.efi", ba)
+	if err != nil {
+		return
+	}
+
+	if false {
+		// TODO
+		ba, err = grubMk("i386-pc")
+		if err != nil {
+			return err
+		}
+
+		arch.WriteHeader(&tar.Header{
+			Name: "grub.img",
+			Size: int64(len(ba)),
+		})
+		arch.Write(ba)
+	}
+
+	// config
+	cfgBytes, cfg, err := ctx.Config()
+	if err != nil {
+		return err
+	}
+
+	archAdd("config.yaml", cfgBytes)
+
+	// kernel and initrd
+	type distCopy struct {
+		Src []string
+		Dst string
+	}
+
+	copies := []distCopy{
+		// XXX {Src: []string{"kernels", ctx.Group.Kernel}, Dst: "current/vmlinuz"},
+		// XXX {Src: []string{"initrd", ctx.Group.Initrd}, Dst: "current/initrd"},
+	}
+
+	// layers
+	for _, layer := range cfg.Layers {
+		layerVersion := ctx.Group.Versions[layer]
+		if layerVersion == "" {
+			return fmt.Errorf("layer %q not mapped to a version", layer)
+		}
+
+		copies = append(copies,
+			distCopy{
+				Src: []string{"layers", layer, layerVersion},
+				Dst: filepath.Join("current", "layers", layer+".fs"),
+			})
+	}
+
+	for _, copy := range copies {
+		outPath, err := ctx.distFetch(copy.Src...)
+		if err != nil {
+			return err
+		}
+
+		f, err := os.Open(outPath)
+		if err != nil {
+			return err
+		}
+
+		defer f.Close()
+
+		stat, err := f.Stat()
+		if err != nil {
+			return err
+		}
+
+		if err = arch.WriteHeader(&tar.Header{
+			Name: copy.Dst,
+			Size: stat.Size(),
+		}); err != nil {
+			return err
+		}
+
+		_, err = io.Copy(arch, f)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
diff --git a/cas-cleaner.go b/cas-cleaner.go
index 507e4d9..a3be6ff 100644
--- a/cas-cleaner.go
+++ b/cas-cleaner.go
@@ -31,7 +31,10 @@ func cleanCAS() error {
 	activeTags := make([]string, len(cfg.Hosts))
 
 	for i, host := range cfg.Hosts {
-		ctx := newRenderContext(host, cfg)
+		ctx, err := newRenderContext(host, cfg)
+		if err != nil {
+			return err
+		}
 
 		tag, err := ctx.Tag()
 		if err != nil {
diff --git a/http.go b/http.go
index c6ddf08..4dced7a 100644
--- a/http.go
+++ b/http.go
@@ -93,12 +93,7 @@ func serveHosts(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	hostNames := make([]string, len(cfg.Hosts))
-	for i, host := range cfg.Hosts {
-		hostNames[i] = host.Name
-	}
-
-	renderJSON(w, hostNames)
+	renderJSON(w, cfg.Hosts)
 }
 
 func serveHost(w http.ResponseWriter, r *http.Request) {
@@ -137,7 +132,12 @@ func serveHost(w http.ResponseWriter, r *http.Request) {
 }
 
 func renderHost(w http.ResponseWriter, r *http.Request, what string, host *clustersconfig.Host, cfg *clustersconfig.Config) {
-	ctx := newRenderContext(host, cfg)
+	ctx, err := newRenderContext(host, cfg)
+	if err != nil {
+		log.Printf("host %s: %s: failed to render: %v", what, host.Name, err)
+		http.Error(w, "", http.StatusServiceUnavailable)
+		return
+	}
 
 	switch what {
 	case "ipxe":
@@ -148,8 +148,6 @@ func renderHost(w http.ResponseWriter, r *http.Request, what string, host *clust
 		w.Header().Set("Content-Type", "application/octet-stream")
 	}
 
-	var err error
-
 	switch what {
 	case "ipxe":
 		err = renderIPXE(w, ctx)
@@ -163,6 +161,9 @@ func renderHost(w http.ResponseWriter, r *http.Request, what string, host *clust
 	case "boot.iso":
 		err = renderCtx(w, r, ctx, "boot.iso", buildBootISO)
 
+	case "boot.tar":
+		err = renderCtx(w, r, ctx, "boot.tar", buildBootTar)
+
 	case "config":
 		err = renderConfig(w, r, ctx)
 
diff --git a/install-on-metal.sh b/install-on-metal.sh
new file mode 100755
index 0000000..fa1111c
--- /dev/null
+++ b/install-on-metal.sh
@@ -0,0 +1,37 @@
+#! /bin/sh
+
+if [ $# -ne 2 ]; then
+    echo "USAGE: $0 <device> <tar url>"
+fi
+
+dev=$1
+tar_url=$2
+
+: ${MP:=/mnt}
+
+set -ex
+
+[[ $dev =~ nvme ]] &&
+    devp=${dev}p ||
+    devp=${dev}
+
+vgdisplay storage || {
+    sgdisk --clear $dev
+    sgdisk \
+        --new=0:4096:+2G --typecode=0:EF00 -c 0:boot \
+        --new=0:0:+2M    --typecode=0:EF02 -c 0:BIOS-BOOT  \
+        --new=0:0:0      --typecode=0:FFFF -c 0:data \
+        --hybrid=1:2 \
+        --print $dev
+
+    mkfs.vfat -n DKLBOOT ${devp}1
+
+    pvcreate ${devp}3
+    vgcreate storage ${devp}3
+}
+
+while umount $MP; do true; done
+
+mount -t vfat ${devp}1 $MP
+curl $tar_url |tar xv -C $MP
+umount $MP
diff --git a/render-context.go b/render-context.go
index 02dbd14..4cff7d9 100644
--- a/render-context.go
+++ b/render-context.go
@@ -30,9 +30,16 @@ type renderContext struct {
 	clusterConfig *clustersconfig.Config
 }
 
-func newRenderContext(host *clustersconfig.Host, cfg *clustersconfig.Config) *renderContext {
-	group := cfg.Group(host.Group)
+func newRenderContext(host *clustersconfig.Host, cfg *clustersconfig.Config) (*renderContext, error) {
 	cluster := cfg.Cluster(host.Cluster)
+	if cluster == nil {
+		return nil, fmt.Errorf("no cluster named %q", host.Cluster)
+	}
+
+	group := cfg.Group(host.Group)
+	if group == nil {
+		return nil, fmt.Errorf("no group named %q", host.Group)
+	}
 
 	vars := make(map[string]interface{})
 
@@ -55,7 +62,7 @@ func newRenderContext(host *clustersconfig.Host, cfg *clustersconfig.Config) *re
 		StaticPodsTemplate: cfg.StaticPodsTemplate(group.StaticPods),
 
 		clusterConfig: cfg,
-	}
+	}, nil
 }
 
 func (ctx *renderContext) Config() (ba []byte, cfg *config.Config, err error) {