Download Apache ZooKeeper "3.9.3": http://zookeeper.apache.org/releases.html

In the following, we will install ZooKeeper in 3 different hosts: "zkhost1", "zkhost2", and "zkhost3"

On each host, extract the file "apache-zookeeper-3.9.3-bin.tar.gz" in the folder you want to install ZooKeeper:
► /opt/apache-zookeeper-3.9.3-bin

$ tar -xf apache-zookeeper-3.9.3-bin.tar.gz -C /opt/
Optional: Create a symbolic link of the ZooKeeper installation folder:
$ ln -s /opt/apache-zookeeper-3.9.3-bin/ /opt/zookeeper
Change the folders permissions (if needed):
$ chmod -R 755 /opt/apache-zookeeper-3.9.3-bin/ $ sudo chown -R mtitek:mtitek /opt/apache-zookeeper-3.9.3-bin/ $ sudo chown -R mtitek:mtitek /opt/zookeeper

On each host ("zkhost1", "zkhost2", and "zkhost3"), do the following:

Create the data and logs directories:

• Create the folder "data": "/opt/zookeeper/data"
  $ mkdir /opt/zookeeper/data
  
• Create the folder "data-log": "/opt/zookeeper/data-log"
  $ mkdir /opt/zookeeper/data-log
  
• Create the log folder: "/opt/zookeeper/logs"
  $ mkdir /opt/zookeeper/logs
  
• Copy the file "/opt/zookeeper/conf/zoo_sample.cfg" to "/opt/zookeeper/conf/zoo.cfg"
  $ cp /opt/zookeeper/conf/zoo_sample.cfg /opt/zookeeper/conf/zoo.cfg
  

Initialize the server id for each ZooKeeper instance:

• First instance ("zkhost1"):
  $ echo "1" > /opt/zookeeper/data/myid
  
• Second instance ("zkhost2"):
  $ echo "2" > /opt/zookeeper/data/myid
  
• Third instance ("zkhost3"):
  $ echo "3" > /opt/zookeeper/data/myid
  

Adjust the configuration file "conf/zoo.cfg":

• Define the property "dataDir": dataDir=/opt/zookeeper/data
  
  
• Define the property "dataLogDir": dataLogDir=/opt/zookeeper/data-log
  
  
• Add a static configuration for each ZooKeeper instance on the 3 hosts:
  server.1=zkhost1:2888:3888:participant;0.0.0.0:2181 server.2=zkhost2:2888:3888:participant;0.0.0.0:2181 server.3=zkhost3:2888:3888:participant;0.0.0.0:2181
  
• Remove the properties "clientPort" and "clientPortAddress".
  You should not include these parameters in the ZooKeeper configuration "conf/zoo.cfg" file. They should be part of the ZooKeeper instances configuration (see above).
  
  

Example: ZooKeeper configuration file "zoo.cfg" (/opt/zookeeper/conf/zoo.cfg)
# The number of milliseconds of each tick. tickTime=2000 # The number of ticks that the initial synchronization phase can take. initLimit=10 # The number of ticks that can pass between sending a request and getting an acknowledgement. syncLimit=5 # The directory where the snapshot data is stored. dataDir=/opt/zookeeper/data # The directory the transaction log of updates is stored. dataLogDir=/opt/zookeeper/data-log # the port at which the clients will connect: 2181 # the port address at which the clients will connect: 0.0.0.0 server.1=zkhost1:2888:3888:participant;0.0.0.0:2181 server.2=zkhost2:2888:3888:participant;0.0.0.0:2181 server.3=zkhost3:2888:3888:participant;0.0.0.0:2181

To start ZooKeeper instances, run the following command on each host:
$ /opt/zookeeper/bin/zkServer.sh start
To stop ZooKeeper instances, run the following command on each host:
$ /opt/zookeeper/bin/zkServer.sh stop