diff --git a/README.md b/README.md
index 68d514a..1c7e7c8 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,7 @@ rsync -a dist/ /path/to/sd/
 - Docker Compose
 - curl
 - grep
+- gzip
 - jq
 - ruby
 - ssh-keygen
diff --git a/apkovl/etc/fstab b/apkovl/etc/fstab
new file mode 100644
index 0000000..ce7b968
--- /dev/null
+++ b/apkovl/etc/fstab
@@ -0,0 +1,4 @@
+/dev/usbdisk	/media/usb	vfat	noauto	0 0
+/dev/mmcblk0p1	/media/mmcblk0p1	vfat	rw,remount	0 0
+/media/mmcblk0p1/overlay.img	/media/overlay	ext4	rw,relatime,errors=remount-ro	0 0
+overlay	/usr	overlay	lowerdir=/usr,upperdir=/media/overlay/upper/usr,workdir=/media/overlay/work/usr	0 0
diff --git a/bin/build b/bin/build
index 20d98f5..1b2eef5 100755
--- a/bin/build
+++ b/bin/build
@@ -12,4 +12,6 @@ bin/download "${version}" dist
 docker-compose run --rm minirootfs sh -c 'apk update && apk add'
 ssh-keygen -A -f apkovl
 cp -a usercfg.txt cache -t dist
+gzip -cdk overlay.img.gz > dist/overlay.img
+docker-compose run --rm builder
 tar czf dist/localhost.apkovl.tar.gz --owner=0 --group=0 -C apkovl .
diff --git a/docker-compose.yml b/docker-compose.yml
index 3857524..f59e17d 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -6,3 +6,17 @@ services:
       - ./cache:/etc/apk/cache
       - ./apkovl/etc/apk/repositories:/etc/apk/repositories
       - ./apkovl/etc/apk/world:/etc/apk/world
+  builder:
+    image: ghcr.io/kou029w/yama/minirootfs
+    volumes:
+      - ./cache:/etc/apk/cache
+      - ./apkovl/etc/apk/repositories:/etc/apk/repositories
+      - ./apkovl/etc/apk/world:/etc/apk/world
+      - ./fstab:/etc/fstab
+      - ./dist/overlay.img:/overlay.img
+    privileged: true
+    command: |
+      sh -c '
+        mount -a \
+          && apk add g++ linux-headers make nodejs npm python3
+      '
diff --git a/fstab b/fstab
new file mode 100644
index 0000000..5618065
--- /dev/null
+++ b/fstab
@@ -0,0 +1,2 @@
+/overlay.img	/mnt	ext4	rw,relatime,errors=remount-ro	0 0
+overlay	/usr	overlay	lowerdir=/usr,upperdir=/mnt/upper/usr,workdir=/mnt/work/usr	0 0
diff --git a/overlay.img.gz b/overlay.img.gz
new file mode 100644
index 0000000..1b6992b
Binary files /dev/null and b/overlay.img.gz differ