diff --git a/docker/Dockerfile b/docker/Dockerfile
index e714896..e0080a2 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -9,7 +9,7 @@
 ENV DASH_HOME /srv/dash
 
 RUN apk update
-RUN apk add scapy
+RUN apk add scapy tcpdump
 #RUN apt-get update -qq && apt-get install -qq -y python-scapy tcpdump tcpreplay wireshark python-requests
 RUN rm -rf /var/cache/apk/*
 
diff --git a/docker/docker-entrypoint.sh b/docker/docker-entrypoint.sh
index d9d4bac..453529e 100644
--- a/docker/docker-entrypoint.sh
+++ b/docker/docker-entrypoint.sh
@@ -1,14 +1,14 @@
-#!/bin/bash
+#!/bin/sh
 set -e
 
 # check for exisitng user and create it if necessary
 if ! id -u dash >/dev/null 2>&1; then
 	echo "create dash user"
-	adduser -u 1000 -D -g '' -h $DASH_HOME dash
+	adduser -u 1000 -D -g '' -h ${DASH_HOME} dash
 fi
 
 # update user rights
-chown -R dash:dash $DASH_HOME
+chown -R dash:dash ${DASH_HOME}
 
 exec "$@"