diff --git a/.gitignore b/.gitignore
index 96a23b6..8233806 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@ postrun.sh
 .pc
 *-pc
 apt-cacher-ng/
+.customvars
diff --git a/build-docker.sh b/build-docker.sh
index 79b68d4..2141451 100755
--- a/build-docker.sh
+++ b/build-docker.sh
@@ -5,6 +5,10 @@ BUILD_OPTS="$*"
 
 DOCKER="docker"
 
+# Ensure that any config variables we passed in are written to an env_file
+# so invocations in subsquent shells preserve these values
+printenv | grep 'FWVERSION=\|SERIAL=\|ROOTUSER\|ROOTUSERPASS' > "$DIR/.customvars"
+
 if ! ${DOCKER} ps >/dev/null 2>&1; then
 	DOCKER="sudo docker"
 fi
@@ -79,6 +83,7 @@ if [ "${CONTAINER_EXISTS}" != "" ]; then
 	time ${DOCKER} run --rm --privileged \
 		--volume "${CONFIG_FILE}":/config:ro \
 		-e "GIT_HASH=${GIT_HASH}" \
+		--env-file=${DIR}/.customvars \
 		--volumes-from="${CONTAINER_NAME}" --name "${CONTAINER_NAME}_cont" \
 		pi-gen \
 		bash -e -o pipefail -c "dpkg-reconfigure qemu-user-static &&
@@ -90,6 +95,7 @@ else
 	time ${DOCKER} run --name "${CONTAINER_NAME}" --privileged \
 		--volume "${CONFIG_FILE}":/config:ro \
 		-e "GIT_HASH=${GIT_HASH}" \
+		--env-file=${DIR}/.customvars \
 		pi-gen \
 		bash -e -o pipefail -c "dpkg-reconfigure qemu-user-static &&
 	cd /pi-gen; ./build.sh ${BUILD_OPTS} &&
diff --git a/config b/config
old mode 100644
new mode 100755
index b79c3c8..1525ac0
--- a/config
+++ b/config
@@ -1,6 +1,6 @@
-# Override these values by setting FWVERSION, SERIAL, ROOTUSER 
-# and ROOTUSERPASS before invoking build(-docker).sh like so: 
-# FWVERSION=3 SERIAL=0001 ./build-docker.sh
+# Override these values by optionally setting FWVERSION, SERIAL, 
+# ROOTUSER and ROOTUSERPASS before invoking build(-docker).sh like so: 
+# FWVERSION="XX.YY.ZZZ" SERIAL="XXXXXXXXXXXX" ./build-docker.sh
 
 export IMG_NAME="moab-fw-${FWVERSION:=dev}"
 echo "IMG_NAME is $IMG_NAME"
@@ -12,7 +12,7 @@ TIMEZONE=$(cat /etc/timezone)
 export TIMEZONE_DEFAULT=$TIMEZONE
 echo "TIMEZONE_DEFAULT is $TIMEZONE_DEFAULT"
 
-export LOCALE_DEFAULT=$(cat /etc/default/locale)
+export LOCALE_DEFAULT=${LANG:="en_US.UTF-8"}
 echo "LOCALE_DEFAULT is $LOCALE_DEFAULT"
 
 export FIRST_USER_NAME=${ROOTUSER:="pi"}
diff --git a/export-image/prerun.sh b/export-image/prerun.sh
index 01f1e74..a984c99 100755
--- a/export-image/prerun.sh
+++ b/export-image/prerun.sh
@@ -39,10 +39,6 @@ BOOT_LENGTH=$(echo "$PARTED_OUT" | grep -e '^1:' | cut -d':' -f 4 | tr -d B)
 ROOT_OFFSET=$(echo "$PARTED_OUT" | grep -e '^2:' | cut -d':' -f 2 | tr -d B)
 ROOT_LENGTH=$(echo "$PARTED_OUT" | grep -e '^2:' | cut -d':' -f 4 | tr -d B)
 
-# Ensures that freshly created loop devices are available to mount
-# https://github.com/RPi-Distro/pi-gen/issues/320#issuecomment-518484064
-sleep 5
-
 BOOT_DEV=$(losetup --show -f -o "${BOOT_OFFSET}" --sizelimit "${BOOT_LENGTH}" "${IMG_FILE}")
 ROOT_DEV=$(losetup --show -f -o "${ROOT_OFFSET}" --sizelimit "${ROOT_LENGTH}" "${IMG_FILE}")
 echo "/boot: offset $BOOT_OFFSET, length $BOOT_LENGTH"
@@ -57,6 +53,10 @@ done
 mkdosfs -n boot -F 32 -v "$BOOT_DEV" > /dev/null
 mkfs.ext4 -L rootfs -O "$ROOT_FEATURES" "$ROOT_DEV" > /dev/null
 
+# Ensures that freshly created loop devices are available to mount
+# https://github.com/RPi-Distro/pi-gen/issues/320#issuecomment-518484064
+sleep 5
+
 mount -v "$ROOT_DEV" "${ROOTFS_DIR}" -t ext4
 mkdir -p "${ROOTFS_DIR}/boot"
 mount -v "$BOOT_DEV" "${ROOTFS_DIR}/boot" -t vfat
diff --git a/stage2/04-custom-tweaks/00-packages b/stage2/04-custom-tweaks/00-packages
new file mode 100644
index 0000000..cfe86da
--- /dev/null
+++ b/stage2/04-custom-tweaks/00-packages
@@ -0,0 +1 @@
+python3-pip
\ No newline at end of file
diff --git a/stage2/04-custom-tweaks/01-run.sh b/stage2/04-custom-tweaks/01-run.sh
index 1a5614c..b6aef34 100755
--- a/stage2/04-custom-tweaks/01-run.sh
+++ b/stage2/04-custom-tweaks/01-run.sh
@@ -7,4 +7,13 @@ echo "Installing docker..."
 on_chroot << EOF
 curl -sSL get.docker.com | sh
 usermod -aG docker ${FIRST_USER_NAME}
-EOF
\ No newline at end of file
+EOF
+
+# Install docker-compose
+echo "Installing docker-compose"
+on_chroot << EOF
+pip3 install docker-compose
+
+# Ensure it's in PATH
+ln -sfn /home/${FIRST_USER_NAME}/.local/bin/docker-compose /usr/bin/docker-compose
+EOF