# Create compute node group for running compute jobs in AWS PCS
<a name="getting-started_create-cng_workers"></a>

 In this step, you will launch a compute node group that scales elastically to run jobs submitted to the cluster. 

**To create the compute node group**
+ Open the [AWS PCS console](https://console.aws.amazon.com/pcs) and navigate to **Clusters**.
+ Select the cluster named `get-started`
+ Navigate to **Compute node groups** and choose **Create**.
+ In the **Compute node group setup** section, provide the following:
  + **Compute node group name** – Enter `compute-1`.
+ Under **Computing configuration**, enter or select these values:
  + **EC2 launch template** – Choose the launch template where the name is `compute-getstarted-lt`
  + **IAM instance profile** – Choose the instance profile named `AWSPCS-getstarted-role`
  + **Subnets** – Select the subnet where the name starts with `hpc-networking:PrivateSubnetA`. Compute nodes run in a private subnet because they process jobs and do not need to be reachable from the internet.
  + **Instances** – Select `c6i.xlarge`.
  + **Scaling configuration** – For **Min. instance count**, enter `0`. For **Max. instance count**, enter `4`. A minimum of `0` lets AWS PCS scale the group down to no instances when there are no jobs to run, so you pay for compute only when work is queued.
+ Under **Additional settings**, specify the following:
  + **AMI ID** – Select an AMI you want to use, that has a name in the following format:

    ```
    aws-pcs-sample_ami-al2023-{{platform}}-slurm-{{version}}
    ```
**Note**  
Sample AMIs for Slurm 25.05 and previous versions use Amazon Linux 2 (`amzn2`) instead of Amazon Linux 2023 (`al2023`).

    For more information about the sample AMIs, see [Using sample Amazon Machine Images (AMIs) with AWS PCS](working-with_ami_samples.md).
+ In the **Node lifecycle actions** section, add scripts that mount shared storage and forward node logs. Choose **Add script** for each of the following actions. Scripts run from top to bottom within a stage, so add them in the order shown. For more information about the scripts that AWS maintains, see [AWS-maintained scripts](cng-node-lifecycle-actions-vetted-scripts.md).

  1. **configure-cloudwatch-logs** – Forwards each node's lifecycle action logs to Amazon CloudWatch Logs. Configure it first so the actions that follow have their output captured from the node's first boot.
     + **Lifecycle stage** – Select `nodeBootstrapped`.
     + **Script location** – Enter `s3://aws-pcs-repo-{{region}}/aws-pcs-node-lifecycle-scripts/configure-cloudwatch-logs-v1-latest.sh`, replacing {{region}} with your cluster's AWS Region.
     + **Name** – Enter `configure-cloudwatch-logs`.
     + **Arguments** – Leave this field empty. The script automatically sends logs to the `/aws/pcs/{{cluster-id}}/lifecycle` log group.
     + **Error handling behavior** – Select `CONTINUE`.
     + **Execution policy** – Select `FIRST_BOOT_ONLY`.

  1. **configure-efs-homes** – Mounts the Amazon EFS file system as the home-directory base at `/home` and configures the node to create each user's home directory on first login.
     + **Lifecycle stage** – Select `nodeBootstrapped`.
     + **Script location** – Enter `s3://aws-pcs-repo-{{region}}/aws-pcs-node-lifecycle-scripts/configure-efs-homes-v1-latest.sh`, replacing {{region}} with your cluster's AWS Region.
     + **Name** – Enter `configure-efs-homes`.
     + **Arguments** – Enter `--efs-id {{efs-file-system-id}} --home-base /home --options tls`, replacing {{efs-file-system-id}} with the ID of the EFS file system you created earlier in the tutorial.
     + **Error handling behavior** – Select `CONTINUE`.
     + **Execution policy** – Select `EVERY_BOOT`.

  1. **mount-fsx-lustre** – Mounts the FSx for Lustre file system at `/shared` for high-performance shared scratch storage.
     + **Lifecycle stage** – Select `nodeBootstrapped`.
     + **Script location** – Enter `s3://aws-pcs-repo-{{region}}/aws-pcs-node-lifecycle-scripts/mount-fsx-lustre-v1-latest.sh`, replacing {{region}} with your cluster's AWS Region (for example, `us-east-1`).
     + **Name** – Enter `mount-fsx-lustre`.
     + **Arguments** – Enter `--fsx-dns-name {{fsx-dns-name}} --mount-name {{mount-name}} --mount-point /shared`, replacing {{fsx-dns-name}} with the **DNS name** and {{mount-name}} with the **Mount name** that you noted when you created the FSx for Lustre file system.
     + **Error handling behavior** – Select `CONTINUE`.
     + **Execution policy** – Select `EVERY_BOOT`.

  1. **set-shared-dir-mode** – Sets `/shared` to world-writable, sticky permissions (mode `1777`) so that any user can create files in it. It runs after `mount-fsx-lustre` so that it applies to the mounted file system.
     + **Lifecycle stage** – Select `nodeBootstrapped`.
     + **Script location** – Enter `https://aws-hpc-recipes.s3.us-east-1.amazonaws.com/main/recipes/pcs-scripts/open_shared_dir/assets/set-shared-dir-mode-v1.0.0.sh`. This community script is published by HPC Recipes for AWS.
     + **Name** – Enter `set-shared-dir-mode`.
     + **Arguments** – Enter `--path /shared --mode 1777`.
     + **Error handling behavior** – Select `CONTINUE`.
     + **Execution policy** – Select `EVERY_BOOT`.
+ Choose **Create compute node group**.

 The **Status** field shows **Creating** while the compute node group is being provisioned.

**Important**  
 Wait for the **Status** field to show **Active** before proceeding to the next step in this tutorial.