first version of hadoop-base hadoop-namenode and hadoop-datanode

README.md

@@ -1 +1,29 @@
-this will be the repo for docker-hadoop
+This is a docker container for hadoop. 
+
+By default it uses data replication "2". To change it edit the hdfs-site.xml file.
+
+To start the namenode run 
+
+    docker run --name namenode -h bde2020/hadoop-namenode
+
+To start two datanodes on the same host run
+
+    docker run --name datanode1 --link namenode:namenode bde2020/hadoop-datanode
+    docker run --name datanode2 --link namenode:namenode bde2020/hadoop-datanode
+    
+More info is comming soon on how to run hadoop docker using docker network and docker swarm
+
+All data are stored in /hdfs-data, so to store data in a host directory datanodes as
+
+    docker run --name datanode1 --link namenode:namenode -v /path/to/host:/hdfs-data bde2020/hadoop-datanode
+    docker run --name datanode2 --link namenode:namenode -v /path/to/host:/hdfs-data bde2020/hadoop-datanode
+
+By default the namenode formats the namenode directory only if not exists (hdfs namenode -format -nonInteractive). 
+If you want to mount an external directory that already contains a namenode directory and format it you have to first delete it manually.
+
+Hadoop namenode listens on 
+
+    hdfs://namenode:8020
+    
+To use access the namenode from another container link it using "--link namenode:namenode" and then use the afformentioned URL.
+More info on how to access it using docker network coming soon.