diff --git a/Makefile b/Makefile
index ed3aca3..5e51e01 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,9 @@
-update.tar: output/update.tar.zstd
+O ?= .
+IMAGESDIR ?= $(O)/images
 
-.prepared: \
+update.tar: $(IMAGESDIR)/update.tar.zstd
+
+$(O)/.prepared: \
 		prepare.sh \
 		config-portage.sh \
 		setup-local-repo.sh \
@@ -9,86 +12,87 @@ update.tar: output/update.tar.zstd
 	./prepare.sh
 	./config-portage.sh
 	./setup-local-repo.sh
-	touch .prepared
+	mkdir -p $(O)
+	touch $(O)/.prepared
 
-prepare: .prepared
+prepare: $(O)/.prepared
 
-.host-tools: \
+$(O)/.host-tools: \
 		build-host-tools.sh \
-		.prepared
+		$(O)/.prepared
 	./build-host-tools.sh
-	touch .host-tools
+	touch $(O)/.host-tools
 
-host-tools: .host-tools
+host-tools: $(O)/.host-tools
 
-.built: \
+$(O)/.built: \
 		build.sh \
 		build-rootfs.sh \
-		linux/arch/arm64/boot/Image.gz \
-		.host-tools \
-		.prepared
+		$(O)/linux/arch/arm64/boot/Image.gz \
+		$(O)/.host-tools \
+		$(O)/.prepared
 	./build.sh
 	./build-rootfs.sh
-	touch .built
+	touch $(O)/.built
 
-images/rootfs.squashfs: \
+$(IMAGESDIR)/rootfs.squashfs: \
 		build-squashfs.sh \
 		squashfs.exclude \
-		.built
-	./build-squashfs.sh
+		$(O)/.built
+	./build-squashfs.sh "$(IMAGESDIR)"
 
-squashfs: images/rootfs.squashfs
+squashfs: $(IMAGESDIR)/rootfs.squashfs
 
-linux/arch/arm64/boot/Image.gz: \
+$(O)/linux/arch/arm64/boot/Image.gz: \
 		build-kernel.sh \
 		linux.config \
-		.host-tools \
-		.prepared
-	./build-kernel.sh
+		$(O)/.host-tools \
+		$(O)/.prepared
+	./build-kernel.sh "$(O)"
 
-kernel: linux/arch/arm64/boot/Image.gz
+kernel: $(O)/linux/arch/arm64/boot/Image.gz
 
-output/efi-part/EFI/BOOT/BOOTAA64.efi: \
+$(O)/efi-part/EFI/BOOT/BOOTAA64.efi: \
 		build-grub.sh \
 		grub.cfg \
-		.host-tools \
-		.prepared
-	./build-grub.sh
+		$(O)/.host-tools \
+		$(O)/.prepared
+	./build-grub.sh "$(O)"
 
-grub: output/efi-part/EFI/BOOT/BOOTAA64.efi
+grub: $(O)/efi-part/EFI/BOOT/BOOTAA64.efi
 
-output/efi-part/u-boot.bin: \
+$(O)/efi-part/u-boot.bin: \
 		build-uboot.sh \
 		u-boot.config
-	./build-uboot.sh
+	./build-uboot.sh "$(O)"
 
-uboot: output/efi-part/u-boot.bin
+uboot: $(O)/efi-part/u-boot.bin
 
-images/sdcard.img: \
+$(IMAGESDIR)/sdcard.img: \
 		genimage.cfg \
 		genimage.sh \
 		post-build.sh \
-		output/efi-part/u-boot.bin \
-		output/efi-part/EFI/BOOT/BOOTAA64.efi
-	./post-build.sh
-	./genimage.sh
+		$(O)/efi-part/u-boot.bin \
+		$(O)/efi-part/EFI/BOOT/BOOTAA64.efi
+	./post-build.sh "$(O)"
+	./genimage.sh "$(O)" "$(IMAGESDIR)"
 
-sdcard.img: images/sdcard.img
+sdcard.img: $(IMAGESDIR)/sdcard.img
 
-images/firmware.img: images/sdcard.img
+$(IMAGESDIR)/firmware.img: $(IMAGESDIR)/sdcard.img
 
-output/update.tar.zstd: \
-		images/rootfs.squashfs \
-		images/firmware.img \
+$(IMAGESDIR)/update.tar.zstd: \
+		$(IMAGESDIR)/rootfs.squashfs \
+		$(IMAGESDIR)/firmware.img \
 		install-update.sh \
-		.host-tools \
-		.prepared
-	./build-update.sh
+		$(O)/.host-tools \
+		$(O)/.prepared
+	./build-update.sh "$(IMAGESDIR)"
 
 clean:
 	git -C u-boot clean -fdx && git -C u-boot checkout -- .
-	rm -rf linux output images tmp
-	rm -f .prepared .host-tools
+	rm -rf $(O)/linux $(O)/output $(IMAGESDIR) $(O)/tmp
+	rm -f $(O)/.prepared $(O)/.host-tools
 
 .PHONY: \
 	grub \
diff --git a/build-grub.sh b/build-grub.sh
index 4d53937..ac2fe2a 100755
--- a/build-grub.sh
+++ b/build-grub.sh
@@ -5,6 +5,8 @@ set -e
 
 . ./config
 
+O="${1}"
+
 GRUB_MODULES='
 boot
 echo
@@ -26,17 +28,17 @@ zstd
 '
 
 echo 'Creating GRUB image ...'
-mkdir -p output/efi-part/EFI/BOOT
+mkdir -p "${O}"/efi-part/EFI/BOOT
 grub-mkimage \
     -O arm64-efi \
-    -o output/efi-part/EFI/BOOT/BOOTAA64.efi \
+    -o "${O}"/efi-part/EFI/BOOT/BOOTAA64.efi \
     -d /usr/${target}/usr/lib/grub/arm64-efi \
     -p /EFI/gentoo \
     ${GRUB_MODULES}
 
 echo 'Generating GRUB configuration file ...'
-mkdir -p output/efi-part/EFI/gentoo
-cp -uv grub.cfg output/efi-part/EFI/gentoo
-grub-editenv output/efi-part/EFI/gentoo/grubenv set rootflags='ro'
-grub-editenv output/efi-part/EFI/gentoo/grubenv set default=0
-grub-editenv output/efi-part/EFI/gentoo/grubenv set timeout=5
+mkdir -p "${O}"/efi-part/EFI/gentoo
+cp -uv grub.cfg "${O}"/efi-part/EFI/gentoo
+grub-editenv "${O}"/efi-part/EFI/gentoo/grubenv set rootflags='ro'
+grub-editenv "${O}"/efi-part/EFI/gentoo/grubenv set default=0
+grub-editenv "${O}"/efi-part/EFI/gentoo/grubenv set timeout=5
diff --git a/build-kernel.sh b/build-kernel.sh
index 2836cc1..cb06477 100755
--- a/build-kernel.sh
+++ b/build-kernel.sh
@@ -3,16 +3,20 @@
 
 set -e
 
+O="${1}"
+
 . ./config
 
 emerge -vnj ${kernel_pkg}
 
 export ARCH=arm64 CROSS_COMPILE=${target}-
-mkdir -p linux
-cd linux
+unset MAKEFLAGS MAKEOVERRIDES MAKELEVEL
+mkdir -p "${O}"/linux
 /usr/src/linux/scripts/kconfig/merge_config.sh -m \
+    -O "${O}"/linux \
     /usr/src/linux/arch/*/configs/${kernel_defconfig}_defconfig \
-    ../linux.config
+    linux.config
+cd "${O}"/linux
 make -C /usr/src/linux O=${PWD} olddefconfig
 make -j$(nproc)
 touch arch/arm64/boot/Image.gz
@@ -22,14 +26,14 @@ cd -
 
 printf 'Installing Kernel %s ...\n' "${kver}"
 mkdir -p /mnt/gentoo/boot
-cp -au linux/arch/arm64/boot/Image.gz /mnt/gentoo/boot/vmlinuz-${kver}
-cp -au linux/.config /mnt/gentoo/boot/config-${kver}
-cp -au linux/System.map /mnt/gentoo/boot/System.map-${kver}
+cp -au "${O}"/linux/arch/arm64/boot/Image.gz /mnt/gentoo/boot/vmlinuz-${kver}
+cp -au "${O}"/linux/.config /mnt/gentoo/boot/config-${kver}
+cp -au "${O}"/linux/System.map /mnt/gentoo/boot/System.map-${kver}
 
 printf 'Installing device tree binaries ...\n'
-mkdir -p output/efi-part/overlays
-cp -au linux/arch/arm64/boot/dts/${device_tree} output/efi-part/
-cp -au \
-    linux/arch/arm64/boot/dts/overlays/*.dtb \
-    linux/arch/arm64/boot/dts/overlays/*.dtbo \
-    output/efi-part/overlays/
+mkdir -p "${O}"/efi-part/overlays
+cp -u "${O}"/linux/arch/arm64/boot/dts/${device_tree} "${O}"/efi-part/
+cp -u \
+    "${O}"/linux/arch/arm64/boot/dts/overlays/*.dtb \
+    "${O}"/linux/arch/arm64/boot/dts/overlays/*.dtbo \
+    "${O}"/efi-part/overlays/
diff --git a/build-squashfs.sh b/build-squashfs.sh
index e8863b7..863721a 100755
--- a/build-squashfs.sh
+++ b/build-squashfs.sh
@@ -5,10 +5,12 @@ set -e
 
 . ./config
 
-mkdir -p images
+IMAGESDIR="${1}"
+
+mkdir -p "${IMAGESDIR}"
 mksquashfs \
     /mnt/gentoo \
-    images/rootfs.squashfs \
+    "${IMAGESDIR}"/rootfs.squashfs \
     -comp gzip \
     -ef squashfs.exclude \
     -no-exports \
diff --git a/build-uboot.sh b/build-uboot.sh
index 01c0fcb..60f9f7b 100755
--- a/build-uboot.sh
+++ b/build-uboot.sh
@@ -5,12 +5,14 @@ set -e
 
 . ./config
 
+O="${1}"
+
 ./patch-uboot.sh
 cd u-boot
 cat configs/rpi_4_defconfig ../u-boot.config > configs/yellow_defconfig
-make yellow_defconfig
-CROSS_COMPILE=${target}- make
+make O="${O}"/u-boot yellow_defconfig
+CROSS_COMPILE=${target}- make O="${O}"/u-boot -j$(nproc)
 cd ..
 
-mkdir -p output/efi-part
-cp -au u-boot/u-boot.bin output/efi-part
+mkdir -p "${O}"/efi-part
+cp -u "${O}"/u-boot/u-boot.bin "${O}"/efi-part
diff --git a/build-update.sh b/build-update.sh
index 68b659e..029c8e7 100755
--- a/build-update.sh
+++ b/build-update.sh
@@ -5,11 +5,13 @@ set -e
 
 . ./config
 
-cd images
+IMAGESDIR="$1"
+
+cd "${IMAGESDIR}"
 sha256sum firmware.img > digests
 sha256sum rootfs.squashfs >> digests
-ln ../install-update.sh install
-tar -c --zstd -f ../output/update.tar.zstd \
+cp -u "${OLDPWD}"/install-update.sh install
+tar -c --zstd -f update.tar.zstd \
     digests \
     firmware.img \
     rootfs.squashfs \
diff --git a/build.sh b/build.sh
index 37da754..03c693a 100755
--- a/build.sh
+++ b/build.sh
@@ -5,6 +5,8 @@ set -e
 
 . ./config
 
+unset MAKEFLAGS MAKEOVERRIDES MAKELEVEL
+
 ${target}-emerge -vuUDj sys-apps/util-linux
 
 ${target}-emerge -vnuUDj \
diff --git a/genimage.cfg b/genimage.cfg
index a91fe70..50b9d3e 100644
--- a/genimage.cfg
+++ b/genimage.cfg
@@ -4,7 +4,7 @@ image firmware.img {
 	vfat {
 	}
 
-	srcpath = "output/efi-part"
+	srcpath = "efi-part"
 	size = 32M
 }
 
diff --git a/genimage.sh b/genimage.sh
index bf32a37..11d556a 100755
--- a/genimage.sh
+++ b/genimage.sh
@@ -14,14 +14,18 @@ cleanup() {
 
 . ./config
 
+O="${1}"
+IMAGESDIR="${2}"
+
 trap cleanup INT TERM QUIT EXIT
 tmproot=$(mktemp -d)
 tmppath=$(mktemp -d)
 
+cd "${O}"
 genimage \
     --rootpath "${tmproot}" \
     --tmppath "${tmppath}" \
-    --inputpath images/ \
-    --outputpath images/ \
+    --inputpath "${IMAGESDIR}" \
+    --outputpath "${IMAGESDIR}" \
     --mkdosfs mkfs.vfat \
-    --config genimage.cfg
+    --config "${OLDPWD}"/genimage.cfg
diff --git a/post-build.sh b/post-build.sh
index cace20e..3e58b47 100755
--- a/post-build.sh
+++ b/post-build.sh
@@ -5,9 +5,9 @@ set -e
 
 . ./config
 
-cp -auv \
+cp -uv \
     /usr/${target}/boot/*.bin \
     /usr/${target}/boot/*.dat \
     /usr/${target}/boot/*.elf \
     config.txt \
-    output/efi-part/
+    "$1"/efi-part/