Add dumb-init for pid 1

Dockerfile

@@ -100,7 +100,7 @@ RUN adduser --no-create-home --uid 1161 --group --system squid \
     && echo "cache_log /var/log/squid/cache.log" >> /etc/squid/squid.conf \
     && echo "cache_effective_user squid" >> /etc/squid/squid.conf \
 # Packages dependencies installation for running and clean again 
-    && apt-get update && apt-get install -y --no-install-recommends ca-certificates net-tools rsync libexpat1 libltdl7 libxml2 openssl ca-certificates libldap-2.4-2 libecap3 libcap2 libdb5.3 libatomic1 \
+    && apt-get update && apt-get install -y --no-install-recommends ca-certificates net-tools rsync libexpat1 libltdl7 libxml2 openssl ca-certificates libldap-2.4-2 libecap3 libcap2 libdb5.3 libatomic1 dumb-init \
     && apt-get auto-remove -y && apt-get clean autoclean \
     && rm -rf /var/lib/apt/lists/* && rm -Rf /tmp/* 
 
@@ -108,4 +108,5 @@ COPY run.sh /
 RUN chmod +x /run.sh
 HEALTHCHECK CMD squidclient mgr:index | grep "HTTP/1.1 200 OK" || exit 1
 EXPOSE 3128
-ENTRYPOINT ["/run.sh"]
+ENTRYPOINT ["dumb-init"]
+CMD ["bash", "-c", "/run.sh && squid -N -n $HOSTNAME"]