dockerfile: added `BIND_DATA_DIR` environment variable

Dockerfile

@@ -5,6 +5,8 @@ ENV DATA_DIR=/data \
     BIND_USER=bind \
     WEBMIN_VERSION=1.740
 
+ENV BIND_DATA_DIR=${DATA_DIR}/bind
+
 RUN rm -rf /etc/apt/apt.conf.d/docker-gzip-indexes \
  && apt-get update \
  && apt-get install -y bind9 perl libnet-ssleay-perl openssl \

start

@@ -6,22 +6,22 @@ WEBMIN_ENABLED=${WEBMIN_ENABLED:-true}
 chmod 775 ${DATA_DIR}
 
 # create directory for bind config
-mkdir -p ${DATA_DIR}/bind
-chown -R root:${BIND_USER} ${DATA_DIR}/bind
+mkdir -p ${BIND_DATA_DIR}
+chown -R root:${BIND_USER} ${BIND_DATA_DIR}
 
 # populate default bind configuration if it does not exist
-if [ ! -d ${DATA_DIR}/bind/etc ]; then
-  mv /etc/bind ${DATA_DIR}/bind/etc
+if [ ! -d ${BIND_DATA_DIR}/etc ]; then
+  mv /etc/bind ${BIND_DATA_DIR}/etc
 fi
 rm -rf /etc/bind
-ln -sf ${DATA_DIR}/bind/etc /etc/bind
+ln -sf ${BIND_DATA_DIR}/etc /etc/bind
 
-if [ ! -d ${DATA_DIR}/bind/lib ]; then
-  mkdir -p ${DATA_DIR}/bind/lib
-  chown root:${BIND_USER} ${DATA_DIR}/bind/lib
+if [ ! -d ${BIND_DATA_DIR}/lib ]; then
+  mkdir -p ${BIND_DATA_DIR}/lib
+  chown root:${BIND_USER} ${BIND_DATA_DIR}/lib
 fi
 rm -rf /var/lib/bind
-ln -sf ${DATA_DIR}/bind/lib /var/lib/bind
+ln -sf ${BIND_DATA_DIR}/lib /var/lib/bind
 
 # create directory for webmin
 mkdir -p ${DATA_DIR}/webmin