diff --git a/docker/server/Dockerfile b/docker/server/Dockerfile
index 03bdb73..23c044b 100644
--- a/docker/server/Dockerfile
+++ b/docker/server/Dockerfile
@@ -10,7 +10,8 @@ VOLUME /data
 WORKDIR /data
 
 # running as a named unprivileged user
-RUN addgroup -S user && adduser -S user -G user
+RUN addgroup -S -g 1001 user && adduser -S -u 1001 user -G user
+RUN chown user:user /data
 USER user
 
 COPY ./start.sh /usr/local/bin/
diff --git a/docker/server/start.sh b/docker/server/start.sh
index 75ba3eb..f8b1e40 100755
--- a/docker/server/start.sh
+++ b/docker/server/start.sh
@@ -3,6 +3,14 @@
 # Download if necessary a file
 if [ ! -z "$DOWNLOAD" ]
 then
+    # Check if /data is writable
+    if [ ! -w /data ]
+    then
+        echo "'/data' directory is not writable by '$(id -n -u):$(id -n -g)' ($(id -u):$(id -g)). ZIM file(s) can not be written."
+        exit 1
+    fi
+
+    # Dwonload ZIM file
     ZIM=`basename $DOWNLOAD`
     wget $DOWNLOAD -O "$ZIM"