Adds dumb-init to avoid any PID 1 issue.

Dockerfile

@@ -6,9 +6,9 @@ COPY mopidy.conf /var/lib/mopidy/.config/mopidy/mopidy.conf
 # Start helper script
 COPY entrypoint.sh /entrypoint.sh
 
-# Official Mopidy install for Debian/Ubuntu along with some extensions
-# (see https://docs.mopidy.com/en/latest/installation/debian/ )
 RUN set -ex \
+    # Official Mopidy install for Debian/Ubuntu along with some extensions
+    # (see https://docs.mopidy.com/en/latest/installation/debian/ )
  && apt-get update \
  && DEBIAN_FRONTEND=noninteractive apt-get install -y \
         curl \
@@ -30,11 +30,18 @@ RUN set -ex \
         Mopidy-GMusic \
         Mopidy-YouTube \
         pyasn1==0.1.8 \
+    # Install dumb-init
+    # https://github.com/Yelp/dumb-init
+ && DUMP_INIT_URI=$(curl -L https://github.com/Yelp/dumb-init/releases/latest | grep -Po '(?<=href=")[^"]+_amd64(?=")') \
+ && curl -Lo /usr/local/bin/dumb-init "https://github.com/$DUMP_INIT_URI" \
+ && chmod +x /usr/local/bin/dumb-init \
+    # Clean-up
  && apt-get purge --auto-remove -y \
         curl \
         gcc \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* ~/.cache \
+    # Limited access rights.
  && chown mopidy:audio -R /var/lib/mopidy/.config \
  && chown mopidy:audio /entrypoint.sh
 
@@ -45,5 +52,5 @@ VOLUME ["/var/lib/mopidy/local", "/var/lib/mopidy/media"]
 
 EXPOSE 6600 6680
 
-ENTRYPOINT ["/entrypoint.sh"]
+ENTRYPOINT ["/usr/local/bin/dumb-init", "/entrypoint.sh"]
 CMD ["/usr/bin/mopidy"]