Fix volume issues by mounting a dir

Extract a pre-existing image there if one doesn't already exist

Dockerfile

@@ -9,30 +9,11 @@ RUN cd /tmp && \
     cp -r qemu-rpi-kernel-*/* /root/qemu-rpi-kernel/ && \
     rm -rf /tmp/* /root/qemu-rpi-kernel/README.md /root/qemu-rpi-kernel/tools
 
-VOLUME /filesystem.img
+VOLUME /data
 
-ENTRYPOINT ["qemu-system-arm"]
-CMD [ \
-  "-M", "versatilepb", \
-  "-cpu", "arm1176", \
-  "-m", "256", \
-  "-hda", "/filesystem.img", \
-  "-net", "nic", \
-  "-net", "user,hostfwd=tcp::5022-:22", \
-  "-dtb", "/root/qemu-rpi-kernel/versatile-pb.dtb", \
-  "-kernel", "/root/qemu-rpi-kernel/kernel-qemu-4.19.50-buster", \
-  "-append", "root=/dev/sda2 panic=1", \
-  "-no-reboot", \
-  "-display", "none", \
-  "-serial", "mon:stdio" \
-]
+ADD ./entrypoint.sh /entrypoint.sh
+ENTRYPOINT ["./entrypoint.sh"]
 
 FROM dockerpi-vm as dockerpi
 LABEL maintainer="Luke Childs <lukechilds123@gmail.com>"
-
-ADD http://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2019-09-30/2019-09-26-raspbian-buster-lite.zip /tmp/filesystem.zip
-
-RUN cd /tmp && \
-    unzip *.zip && \
-    mv *.img /filesystem.img && \
-    rm -rf /tmp/*
+ADD http://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2019-09-30/2019-09-26-raspbian-buster-lite.zip /filesystem.zip

entrypoint.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+image_path="/data/filesystem.img"
+zip_path="/filesystem.zip"
+
+if [ ! -e $image_path ] && [ -e $zip_path ]; then
+    unzip $zip_path
+    mv *.img $image_path
+fi
+
+exec qemu-system-arm \
+  -M versatilepb \
+  -cpu arm1176 \
+  -m 256M \
+  -hda /data/filesystem.img \
+  -net nic \
+  -net user,hostfwd=tcp::5022-:22 \
+  -dtb /root/qemu-rpi-kernel/versatile-pb.dtb \
+  -kernel /root/qemu-rpi-kernel/kernel-qemu-4.19.50-buster \
+  -append "root=/dev/sda2 panic=1" \
+  -no-reboot \
+  -display none \
+  -serial mon:stdio