Lab2.md

docker

In this Lab we are going to use a Docker Container to create second node to the one already installed.

a) We are going to Install Docker in the CentOS VM
b) Create Centos Docker Image using a DockerFile
c) Instantiate a container
c) Use the AmbariUi to add a Node

Install Docker Binaries

CentOS 7

The following steps are to setup docker on CentOS 7.

   $ sudo yum update

   $ curl -sSL https://get.docker.com/ | sh

   $ sudo service docker start

   $ sudo docker run hello-world

To create the docker group and add your user (not needed if you are root user):

• Log into Centos as a user with sudo privileges.
• Create the docker group and add your user.
• sudo usermod -aG docker your_username
• Log out and log back in.
• This ensures your user is running with the correct permissions.
• Verify your work by running docker without sudo.

  $ docker run hello-world

Ensure Docker is running as a service

  sudo chkconfig docker on

Create Docker images

Use the Dockerfile in the repo to create a CentOS image for HDP Slave Node

  $ mkdir dockerimage
  $ cp DockerFile dockerimage/
  $ docker build --file=dockerimage/DockerFile ./dockerimage

• This will list the newly create image

  $ docker images 

• Tag the image

  $docker tag shivajid/centos:hdp23 __imageid__

• Create the docker instance.

  $docker run -it -h node0 -P --privileged=true shivajid/centos:hdp23 /bin/bash

• User CTRL (P+Q) to exit the container. Do not use exit command.

• List all the running containers

  $docker ps
 

• Re-enter the docker

  
      $ docker exec -it __docker_container_name__
   

Setup the ssh keys

$service sshd start
$ssh-copy-id root@node0
$ ifconfig

• Add an entry for node0 to the host /etc/host file
• Update /etc/hosts/ file for node0 Docker Container for ip address mapping for hdpdemo.hortonworks.com

Services on the node may fail to start. It looks for /usr/java/default which is missing. Create an appropriate link to /usr/java/default

Install Slave Node on the docker images

• Use the Ambari wizard to add the docker container.

• Under the Hosts -> Actions

• Choose the name of the host. In our lab case it is node0Select you private ssh key [log into the docker container, cat the id_rsa key and provide the information under Provide your ssh key.

• Ignore the host checks for the lab. (Please take care in your actual lab sessions)


• Select the service (Select atleast the DataNode and NodeManager) 

• Click Next and start the install process  

Issues and Resolution

• If a Service does not start up. Start the individual Service on the node.


Docker Reference Commands

• Stop a container

$docker stop __container_name_OR_id

• Remove a container

$docker rm __container_name_OR_id

• To Validate. The container should be gone

  $ docker ps

• To delete an image. Get the image id from running "docker image"

$docker rmi __image_id

• To Validae. Run

$ docker image