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2.3. Starting Slave Instances

After our master instance is fully operational, we will start the slave nodes, the ones that store the data and perform the work for Hadoop jobs.
  1. Log in to the AWS Management Console if you have not already.
  2. Click on Instances in the left-hand Navigation pane and select your master instance. Copy its Private DNS and note (perhaps write down) its Availability Zone, both which should be listed in the bottom pane.
  3. Click the Launch Instance button in the toolbar at the top.
  4. In the window that pops up:
    1. Click the Community AMIs tab.
    2. Enter the AMI ID (the same one as before) in the search box at the top.
    3. Find that AMI in the list and click the Select button to the right.
  5. In the next pane:
    1. Optionally choose an instance type (see discussion above).
    2. Enter the number of instances you would like to start. If you are just trying out this process for the first time, start 2 instances (you can always add more later by following these steps in this section again).
    3. Pick the same Availability Zone as your master instance.
    4. Click Continue.
  6. In the next pane:
    1. Type the following line into the User Data field: 
      MASTER_HOST=<master's private DNS>
      Replace <master's private DNS> with the value you copied in step 2. Remember to use the Private DNS!
    2. Click Continue.
  7. In the next pane, select the key pair you created for your master host and click Continue.
  8. In the next pane, select only the security group you created for the entire cluster (not the master group) and click Continue.
  9. In the next pane, review your details and click Launch.