systemctl daemon-reload

  562  systemctl status elasticsearch.service
  563  systemctl daemon-reload
  564  systemctl status elasticsearch.service
  565  vim  /etc/systemd/system/multi-user.target.wants/elasticsearch.service
  566  systemctl daemon-reload
  567  systemctl status elasticsearch.service
  568  service  elasticsearch start
  569  history
  570  systemctl disable elasticsearch
  571  systemctl enable elasticsearch
  572  systemctl status elasticsearch.service
  573  less /usr/lib/systemd/system/elasticsearch.service
  574  vim  /etc/systemd/system/multi-user.target.wants/elasticsearch.service
  575  vim /etc/init.d/elasticsearch
  576  systemctl status elasticsearch.service
  577  systemctl daemon-reload
  578  systemctl status elasticsearch.service
  579  vim /etc/init.d/elasticsearch
  580  systemctl status elasticsearch.service
  581  systemctl daemon-reload
  582  systemctl status elasticsearch.service
  583  history
  584  systemctl disable elasticsearch
  585  systemctl enable elasticsearch
  586  systemctl status elasticsearch.service
  587  ps -ef | grep el
  588  service  elasticsearch start
  589  service  elasticsearch status
  590  ps -ef | grep el

hadoop 2.7.1 single node cluster

root@hadoop-master:/myhadoop# export JAVA_HOME=/usr/lib/jvm/java-8-oracle/
root@hadoop-master:/myhadoop# export HADOOP\_PREFIX=/myhadoop/hadoop-2.7.1
root@hadoop-master:/myhadoop# export HADOOP_CONF_DIR=$HADOOP_PREFIX/etc/hadoop

root@hadoop-master:~# vim /myhadoop/hadoop-2.7.1/etc/hadoop/hadoop-env.sh

#export JAVA_HOME=${JAVA_HOME}

export JAVA_HOME=/usr/lib/jvm/java-8-oracle/

If you want to change it globally and at system level;

root@hadoop-master:~# vim /etc/environment

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"

export JAVA_HOME=/usr/lib/jvm/java-8-oracle/

hadoop on ubunte with java 8

1, install java 8
 sudo add-apt-repository ppa:webupd8team/java
 sudo apt-get update
 sudo apt-get install oracle-java8-installer

2, export java

export JAVA_HOME=/usr/lib/jvm/java-8-oracle/

3, download hadoop

wget http://apache.arvixe.com/hadoop/common/stable/hadoop-2.7.1.tar.gz

4, copy xml file

cp hadoop-2.7.1/etc/hadoop/*.xml input/

5, run hadoop

hadoop-2.7.1/bin/hadoop jar hadoop-2.7.1/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.7.1.jar grep input output 'dfs[a-z.]+'