diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..92b1af6
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,10 @@
+from debian:stable
+
+run apt-get update \
+ && apt-get install -y grub2 grub-efi-amd64-bin grub-pc-bin gdisk dosfstools parted udev \
+ && apt-get clean
+
+volume /output
+copy assets /assets
+
+entrypoint ["/assets/build-image"]
diff --git a/assets/build-image b/assets/build-image
index 965de37..246018b 100755
--- a/assets/build-image
+++ b/assets/build-image
@@ -9,34 +9,35 @@ if [ -e $out ]; then
 fi
 
 # create the file
-truncate -s2100M $out
+truncate -s144M $out
 
 # partition it
 sgdisk \
-	--new=0:4096:+2G --typecode=0:EF00 -c 0:boot   \
-	--new=0:0:+2M    --typecode=0:EF02 -c 0:BIOS-BOOT \
+	--new=0:4096:+128M --typecode=0:EF00 -c 0:boot   \
+	--new=0:0:+2M      --typecode=0:EF02 -c 0:BIOS-BOOT \
 	--hybrid=1:2 --print $out
 
 dev=$(losetup --find --show --partscan $out)
 trap "losetup -d $dev" EXIT
 
-devmap=/tmp/devmap
-cat >$devmap <<EOF
-(hd0) $dev
-EOF
-
 # format filesystems
 mkfs.vfat -n BLKBOOT ${dev}p1
 
 # mount
-mkdir -p /mnt
-(
-mount ${dev}p1 /mnt
-trap "umount /mnt" EXIT
+mkdir -p /boot
 
-mkdir -p /mnt/grub
-cp /assets/grub.cfg /mnt/grub
+mount ${dev}p1 /boot
+trap "umount /boot" EXIT
 
-grub-install --target=i386-pc --boot-directory=/mnt $dev
-grub-install --target=x86_64-efi --removable --boot-directory=/mnt --efi-directory=/mnt
-)
+mkdir -p /boot/grub
+cp /assets/grub.cfg /boot/grub
+
+devmap=/boot/grub/device.map
+cat >$devmap <<EOF
+(hd0) $dev
+EOF
+
+grub-install --target=i386-pc $dev
+grub-install --target=x86_64-efi --removable --efi-directory=/boot
+
+rm $devmap
diff --git a/build-chroot b/build-chroot
deleted file mode 100755
index ead34c2..0000000
--- a/build-chroot
+++ /dev/null
@@ -1,18 +0,0 @@
-#! /bin/bash
-
-set -ex
-
-if ! [ -d chroot ]; then
-    mkdir chroot
-    debootstrap --arch amd64 testing chroot http://http.debian.net/debian/
-fi
-
-if ! [ -e chroot/usr/sbin/grub-mkconfig ]; then
-    chroot chroot <<EOF
-set -ex
-apt-get update
-yes |apt-get install -y grub2 grub-efi-amd64-bin grub-pc-bin gdisk dosfstools
-EOF
-fi
-
-rsync -av --delete assets chroot
diff --git a/build-image b/build-image
new file mode 100755
index 0000000..08d56a1
--- /dev/null
+++ b/build-image
@@ -0,0 +1,6 @@
+
+set -ex
+
+docker build -t grub-support .
+docker run --privileged --rm -v $PWD/output:/output --net=host -v /dev:/dev grub-support
+
diff --git a/enter-chroot b/enter-chroot
deleted file mode 100755
index 3cf1c39..0000000
--- a/enter-chroot
+++ /dev/null
@@ -1,19 +0,0 @@
-#! /bin/bash
-
-cleanup() {
-    umount -R chroot
-}
-
-set -ex
-
-mkdir -p chroot/{dev,proc,sys,output} output
-
-mount --bind chroot chroot
-mount --bind output chroot/output
-mount --bind /dev   chroot/dev
-mount --bind /proc  chroot/proc
-mount --bind /sys   chroot/sys
-
-trap cleanup EXIT
-
-chroot chroot "$@"