# Creating a cluster in AWS PCS
<a name="working-with_clusters_create"></a>

This topic provides an overview of available options and describes what to consider when you create a cluster in AWS Parallel Computing Service (AWS PCS). If this is your first time creating an AWS PCS cluster, we recommend you follow [Get started with AWS Parallel Computing Service](getting-started.md). The tutorial can help you create a working HPC system without expanding into all the available options and system architectures that are possible.

**Note**  
After creating a cluster, you can modify many configuration settings without rebuilding your infrastructure. For more information, see [Updating a cluster in AWS PCS](working-with_clusters_update.md).

**Note**  
You can configure custom Slurm settings to implement advanced scheduling policies and resource management. For more information, see [Configuring custom Slurm settings in AWS PCS](slurm-custom-settings.md).

## Prerequisites
<a name="working-with_clusters_create_prereqs"></a>
+  An existing VPC and subnet that meet [AWS PCS Networking](working-with_networking.md) requirements. Before you deploy a cluster for production use, we recommend that you have a thorough understanding of the VPC and subnet requirements. To create a VPC and subnet, see [Creating a VPC for your AWS PCS cluster](working-with_networking_create-vpc.md). 
+  An [IAM principal](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_terms-and-concepts.html) with permissions to create and manage AWS PCS resources. For more information, see [Identity and Access Management for AWS Parallel Computing Service](security-iam.md). 

## Create an AWS PCS cluster
<a name="working-with_clusters_create_cluster"></a>

You can use the AWS Management Console or AWS CLI to create a cluster.

------
#### [ AWS Management Console ]

**To create a cluster**

1.  Open the AWS PCS console at [https://console.aws.amazon.com/pcs/home\$1/clusters](https://console.aws.amazon.com/pcs/home#/clusters) and choose **Create cluster**. 

1.  In the **Cluster setup** section, enter the following fields: 
   +  **Cluster name** – A name for your cluster. The name can contain only alphanumeric characters (case-sensitive) and hyphens. It must start with an alphabetic character and can't be longer than 40 characters. The name must be unique within the AWS Region and AWS account that you're creating the cluster in. 
   +  **Scheduler** – Choose a scheduler and version. For more information, see [Slurm versions in AWS PCS](slurm-versions.md). 
   +  **Controller size** – Choose a size for your controller. This determines how many concurrent jobs and compute nodes can be managed by the AWS PCS cluster. You can only set the controller size when the cluster is created. For more information on sizing, see [Cluster size in AWS PCS](working-with_clusters_size.md). 

1.  In the **Networking** section, select values for the following fields: 
   +  **Network type** – Choose the IP address type for your cluster. Your cluster can use either IPv4 or IPv6, but not both. The VPC and subnets must use the same network address type. The IP address block you use for each subnet must have at least 1 available address. AWS reserves some of the addresses in each subnet. For more information, see [Subnet CIDR blocks](https://docs.aws.amazon.com/vpc/latest/userguide/subnet-sizing.html) in the *Amazon VPC User Guide*. 
   +  **VPC** – Choose an existing VPC that meets AWS PCS requirements. For more information, see [AWS PCS VPC and subnet requirements and considerations](working-with_networking_vpc-requirements.md). After you create the cluster, you can't change its VPC. If no VPCs are listed, you must create one first. 
   +  **Subnet** – All available subnets in the selected VPC are listed. Choose a subnet that meets the AWS PCS subnet requirements. For more information, see [AWS PCS VPC and subnet requirements and considerations](working-with_networking_vpc-requirements.md). We recommend you select a private subnet to avoid exposing your scheduler endpoints to the public internet.
   +  **Security groups** – Specify the security group(s) that you want AWS PCS to associate with the network interfaces it creates for your cluster. You must select at least one security group that allows communication between your cluster and its compute nodes. You can select **Quick create a security group** to have AWS PCS create one with the necessary configuration in your selected VPC, or select an existing security group. For more information, see [Security group requirements and considerations](working-with_networking_sg.md#working-with_networking_sg-requirements). 

1.  (Optional) In the **Slurm accounting configuration** section, you can enable Slurm accounting and set accounting parameters. For more information, see [Slurm accounting in AWS PCS](slurm-accounting.md). 

1.  (Optional) In the **Slurm configuration** section, you can add parameter name and value pairs to configure additional Slurm settings. For a complete list of supported parameters, see [Custom Slurm settings for AWS PCS clusters](slurm-custom-settings-cluster.md).

1.  (Optional) Under **Tags**, add any tags to your AWS PCS cluster. 

1.  Choose **Create cluster**. The **Status** field shows `Creating` while the AWS PCS creates the cluster. This process can take several minutes. 

**Important**  
There can only be 1 cluster in a `Creating` state per AWS Region per AWS account. AWS PCS returns an error if there is already a cluster in a `Creating` state when you try to create a cluster.

------
#### [ AWS CLI ]

**To create a cluster**

1.  Create your cluster with the command that follows. Before running the command, make the following replacements: 
   +  Replace *region* with the ID of the AWS Region that you want to create your cluster in, such as `us-east-1`.
   +  Replace *my-cluster* with a name for your cluster. The name can contain only alphanumeric characters (case-sensitive) and hyphens. It must start with an alphabetic character and can't be longer than 40 characters. The name must be unique within the AWS Region and AWS account where you're creating the cluster. 
   +  Replace *25.05* with any supported version of Slurm. 
**Note**  
AWS PCS currently supports Slurm 25.05 and 24.11.
   +  Replace *SMALL* with any supported cluster size. This determines how many concurrent jobs and compute nodes can be managed by the AWS PCS cluster. It can only be set when the cluster is created. For more information on sizing, see [Cluster size in AWS PCS](working-with_clusters_size.md). 
   + Replace the value for `subnetIds` with your own. We recommend you select a private subnet to avoid exposing your scheduler endpoints to the public internet.
   + Specify the `securityGroupIds` that you want AWS PCS to associate with the network interfaces it creates for your cluster. The security groups must be in the same VPC as the cluster. You must select at least one security group that allows communication between your cluster and its compute nodes. For more information, see [Security group requirements and considerations](working-with_networking_sg.md#working-with_networking_sg-requirements). 

   ```
   aws pcs create-cluster --region region \
       --cluster-name my-cluster \
       --scheduler type=SLURM,version=25.05 \
       --size SMALL \
       --networking subnetIds=subnet-ExampleId1,securityGroupIds=sg-ExampleId1
   ```
   + to use IPv6, add `networkType=IPV6` to the `--networking` configuration.

     ```
       --networking networkType=IPV6,subnetIds=subnet-ExampleId1,securityGroupIds=sg-ExampleId1
     ```
   +  Optionally, you can add the `--slurm-configration` option to customize the Slurm behavior and specify Slurm configuration options. The following example sets the scale-down idle time to 60 minutes (3600 seconds), enables Slurm accounting, and specifies `slurm.conf` settings as the value for `slurmCustomSettings`. For more information, see [Slurm accounting in AWS PCS](slurm-accounting.md).
**Note**  
Accounting is supported for Slurm 24.11 or later.

     ```
     aws pcs create-cluster --region region \
         --cluster-name my-cluster \
         --scheduler type=SLURM,version=25.05 \
         --size SMALL \
         --networking subnetIds=subnet-ExampleId1,securityGroupIds=sg-ExampleId1
         --slurm-configuration scaleDownIdleTimeInSeconds=3600,accounting='{mode=STANDARD}',slurmCustomSettings='[{parameterName=SelectTypeParameters,parameterValue=CR_CPU_Memory}]'
     ```

1. It can take several minutes to provision the cluster. You can query the status of your cluster with the following command. Don’t proceed to creating queues or compute node groups until the cluster’s status field is `ACTIVE`.

   ```
   aws pcs get-cluster --region region --cluster-identifier my-cluster
   ```

**Important**  
There can only be 1 cluster in a `Creating` state per AWS Region per AWS account. AWS PCS returns an error if there is already a cluster in a `Creating` state when you try to create a cluster.

------

**Recommended next steps for your cluster**
+ Add compute node groups.
+ Add queues.
+ Enable logging.