docker: switch to non-root user

docker/Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get update \
  && truncate -s 0 /var/log/*log
 
 RUN apt-get update \
- && apt-get install -y --no-install-recommends make build-essential inotify-tools chromium \
+ && apt-get install -y --no-install-recommends make build-essential inotify-tools chromium gosu \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
  && truncate -s 0 /var/log/*log
@@ -22,5 +22,6 @@ ENV LC_ALL=C
 
 RUN make prepare
 
+
 ENTRYPOINT ["/app/docker/entrypoint.sh"]
 CMD ["watch"]

docker/entrypoint.sh

@@ -1,6 +1,15 @@
 #!/bin/sh
 
+set -u
+set -e
+
 ARGS="$*"
 echo "Arguments: $ARGS"
 
-exec make "$@"
+EXT_UID=${EXT_UID:-999}
+EXT_GID=${EXT_GID:-999}
+
+groupadd -g "$EXT_GID" appuser
+useradd -r -u "$EXT_UID" -g appuser appuser
+
+exec gosu appuser make "$@"