README with instructions is ready

README.md

@@ -1 +1,37 @@
 # Hadoop Docker
+
+To deploy an example HDFS cluster, run:
+```
+  docker network create hadoop
+  docker-compose up
+```
+
+The configuration parameters can be specified in the hadoop.env file or as environmental variables for specific services (e.g. namenode, datanode etc.):
+```
+  CORE_CONF_fs_defaultFS=hdfs://namenode:8020
+```
+
+CORE_CONF corresponds to core-site.xml. fs_defaultFS=hdfs://namenode:8020 will be transformed into:
+```
+  <property><name>fs.defaultFS</name><value>hdfs://namenode:8020</value></property>
+```
+To define dash inside a configuration parameter, use double underscore, such as YARN_CONF_yarn_log___aggregation___enable=true (yarn-site.xml):
+```
+  <property><name>yarn.log-aggregation-enable</name><value>true</value></property>
+```
+
+The available configurations are:
+* /etc/hadoop/core-site.xml CORE_CONF
+* /etc/hadoop/hdfs-site.xml HDFS_CONF
+* /etc/hadoop/yarn-site.xml YARN_CONF
+* /etc/hadoop/httpfs-site.xml HTTPFS_CONF
+* /etc/hadoop/kms-site.xml KMS_CONF
+
+If you need to extend some other configuration file, refer to base/entrypoint.sh bash script.
+
+After starting the example Hadoop cluster, you should be able to access interfaces of all the components (substitute domain names by IP addresses from ```network inspect hadoop``` command):
+* Namenode: http://namenode:50070/dfshealth.html#tab-overview
+* History server: http://historyserver:8188/applicationhistory
+* Datanode: http://datanode:50075/
+* Nodemanager: http://nodemanager:8042/node
+* Resource manager: http://resourcemanager:8088/