Dockerfile: useradd issue fixed

docker/Dockerfile

@@ -66,7 +66,7 @@ RUN echo "docker-titan-STF525" > /etc/hostname \
       xsltproc \
     && DEBIAN_FRONTEND=noninteractive apt-get autoremove --purge -y \
     && DEBIAN_FRONTEND=noninteractive apt-get autoclean \
-    && useradd --create-home --shell /bin/bash --groups sudo username etsi \
+    && useradd --create-home --shell /bin/bash --groups sudo,username etsi \
     && echo "etsi:etsi" | chpasswd \
     && adduser etsi sudo \
     && cd /home/etsi \