Create bootstrap actions to install additional software

You can use a bootstrap action to install additional software or customize the configuration of cluster instances. Bootstrap actions are scripts that run on cluster after Amazon EMR launches the instance using the Amazon Linux Amazon Machine Image (AMI). Bootstrap actions run before Amazon EMR installs the applications that you specify when you create the cluster and before cluster nodes begin processing data. If you add nodes to a running cluster, bootstrap actions also run on those nodes in the same way. You can create custom bootstrap actions and specify them when you create your cluster.

Most predefined bootstrap actions for Amazon EMR AMI versions 2.x and 3.x are not supported in Amazon EMR releases 4.x. For example, configure-Hadoop and configure-daemons are not supported in Amazon EMR release 4.x. Instead, Amazon EMR release 4.x natively provides this functionality. For more information about how to migrate bootstrap actions from Amazon EMR AMI versions 2.x and 3.x to Amazon EMR release 4.x, go to Customizing cluster and application configuration with earlier AMI versions of Amazon EMR in the Amazon EMR Release Guide.

Bootstrap action basics

Bootstrap actions execute as the Hadoop user by default. You can execute a bootstrap action with root privileges by using sudo.

All Amazon EMR management interfaces support bootstrap actions. You can specify up to 16 bootstrap actions per cluster by providing multiple bootstrap-actions parameters from the console, AWS CLI, or API.

From the Amazon EMR console, you can optionally specify a bootstrap action while creating a cluster.

When you use the CLI, you can pass references to bootstrap action scripts to Amazon EMR by adding the --bootstrap-actions parameter when you create the cluster using the create-cluster command.

--bootstrap-actions Path="s3://mybucket/filename",Args=[arg1,arg2]

If the bootstrap action returns a nonzero error code, Amazon EMR treats it as a failure and terminates the instance. If too many instances fail their bootstrap actions, then Amazon EMR terminates the cluster. If just a few instances fail, Amazon EMR attempts to reallocate the failed instances and continue. Use the cluster lastStateChangeReason error code to identify failures caused by a bootstrap action.

Conditionally run a bootstrap action

In order to only run a bootstrap actions on the master node, you can use a custom bootstrap action with some logic to determine if the node is master.

#!/bin/bash
if grep isMaster /mnt/var/lib/info/instance.json | grep false;
then        
    echo "This is not master node, do nothing,exiting"
    exit 0
fi
echo "This is master, continuing to execute script"
# continue with code logic for master node below

The following output will print from a core node.

This is not master node, do nothing, exiting

The following output will print from master node.

This is master, continuing to execute script

To use this logic, upload your bootstrap action, including the above code, to your Amazon S3 bucket. On the AWS CLI, add the --bootstrap-actions parameter to the aws emr create-cluster API call and specify your bootstrap script location as the value of Path.

Shutdown actions

A bootstrap action script can create one or more shutdown actions by writing scripts to the /mnt/var/lib/instance-controller/public/shutdown-actions/ directory. When a cluster is terminated, all the scripts in this directory are executed in parallel. Each script must run and complete within 60 seconds.

Shutdown action scripts are not guaranteed to run if the node terminates with an error.

Note

When using Amazon EMR versions 4.0 and later, you must manually create the /mnt/var/lib/instance-controller/public/shutdown-actions/ directory on the master node. It doesn't exist by default; however, after being created, scripts in this directory nevertheless run before shutdown. For more information about connecting to the Master node to create directories, see Connect to the primary node using SSH.

Use custom bootstrap actions

You can create a custom script to perform a customized bootstrap action. Any of the Amazon EMR interfaces can reference a custom bootstrap action.

Note

For the best performance, we recommend that you store custom bootstrap actions, scripts, and other files that you want to use with Amazon EMR in an Amazon S3 bucket that is in the same AWS Region as your cluster.

Add custom bootstrap actions

Note

We’ve redesigned the Amazon EMR console to make it easier to use. See What's new with the console? to learn about the differences between the old and new console experiences.

New console

To create a cluster with a bootstrap action with the new console

1. Sign in to the AWS Management Console, and open the Amazon EMR console at https://console.aws.amazon.com/emr.

2. Under EMR on EC2 in the left navigation pane, choose Clusters, and then choose Create cluster.

3. Under Bootstrap actions, choose Add to specify a name, script location, and optional arguments for your action. Select Add bootstrap action.

4. Optionally, add more bootstrap actions.

5. Choose any other options that apply to your cluster.

6. To launch your cluster, choose Create cluster.

Old console

To create a cluster with a custom bootstrap action with the old console

1. Navigate to the new Amazon EMR console and select Switch to the old console from the side navigation. For more information on what to expect when you switch to the old console, see Using the old console.

2. Choose Create cluster.

3. Click Go to advanced options.

4. In Create Cluster - Advanced Options, Steps 1 and 2 choose the options as desired and proceed to Step 3: General Cluster Settings.

5. Under Bootstrap Actions select Configure and add to specify the Name, JAR location, and arguments for your bootstrap action. Choose Add.

6. Optionally add more bootstrap actions as desired.

7. Proceed to create the cluster. Your bootstrap action(s) will be performed after the cluster has been provisioned and initialized.

   As long as the cluster's primary node is running, you can connect to the primary node and see the log files that the bootstrap action script generated in the /mnt/var/log/bootstrap-actions/1 directory.

CLI

To create a cluster with a custom bootstrap action with the AWS CLI

When using the AWS CLI to include a bootstrap action, specify the Path and Args as a comma-separated list. The following example doesn't use an arguments list.

• To launch a cluster with a custom bootstrap action, type the following command, replacing myKey with the name of your EC2 key pair. Include --bootstrap-actions as a parameter and specify your bootstrap script location as the value of Path.

  • Linux, UNIX, and Mac OS X users:

    aws emr create-cluster --name "Test cluster" --release-label emr-4.0.0 \
    --use-default-roles --ec2-attributes KeyName=myKey \
    --applications Name=Hive Name=Pig \
    --instance-count 3 --instance-type m5.xlarge \
    --bootstrap-actions Path="s3://elasticmapreduce/bootstrap-actions/download.sh"

  • Windows users:

    aws emr create-cluster --name "Test cluster" --release-label emr-4.2.0 --use-default-roles --ec2-attributes KeyName=myKey --applications Name=Hive Name=Pig --instance-count 3 --instance-type m5.xlarge --bootstrap-actions Path="s3://elasticmapreduce/bootstrap-actions/download.sh"

  When you specify the instance count without using the --instance-groups parameter, a single primary node is launched, and the remaining instances are launched as core nodes. All nodes will use the instance type specified in the command.

  Note

  If you have not previously created the default Amazon EMR service role and EC2 instance profile, type aws emr create-default-roles to create them before typing the create-cluster subcommand.

  For more information on using Amazon EMR commands in the AWS CLI, see https://docs.aws.amazon.com/cli/latest/reference/emr.

Use a custom bootstrap action to copy an object from Amazon S3 to each node

You can use a bootstrap action to copy objects from Amazon S3 to each node in a cluster before your applications are installed. The AWS CLI is installed on each node of a cluster, so your bootstrap action can call AWS CLI commands.

The following example demonstrates a simple bootstrap action script that copies a file, myfile.jar, from Amazon S3 to a local folder, /mnt1/myfolder, on each cluster node. The script is saved to Amazon S3 with the file name copymyfile.sh with the following contents.

#!/bin/bash
aws s3 cp s3://mybucket/myfilefolder/myfile.jar /mnt1/myfolder

When you launch the cluster, you specify the script. The following AWS CLI example demonstrates this:

aws emr create-cluster --name "Test cluster" --release-label emr-5.36.1 \
--use-default-roles --ec2-attributes KeyName=myKey \
--applications Name=Hive Name=Pig \
--instance-count 3 --instance-type m5.xlarge \
--bootstrap-actions Path="s3://mybucket/myscriptfolder/copymyfile.sh"