# `Image` section
<a name="Image-v3"></a>

**Note**  
Unsupported versions of the official AMIs distributed by AWS ParallelCluster will be made unavailable after 18 months of inactivity. These old images contain outdated software and cannot receive support in case of issues. We strongly suggest moving to the latest supported version.

**(Required)** Defines the operating system for the cluster.

```
Image:
  Os: {{string}}
  CustomAmi: {{string}}
```

## `Image` properties
<a name="Image-v3.properties"></a>

`Os` (**Required**, `String`)  
Specifies the operating system to use for the cluster. The supported values are `alinux2`, `alinux2023`, `ubuntu2404`, `ubuntu2204`, `rhel8`, `rocky8`, `rhel9`, `rocky9`.  
If you configure your cluster to use `rhel`, the on-demand cost for any instance type is higher than when you configure your cluster to use other supported operation systems. For more information about pricing, see [On-Demand Pricing ](https://aws.amazon.com/ec2/pricing/on-demand) and [How is Red Hat Enterprise Linux on Amazon EC2 offered and priced?](https://aws.amazon.com/partners/redhat/faqs/#Pricing_and_Billing). 
Red Hat Enterprise Linux 8.7 (`rhel8`) is added starting in AWS ParallelCluster version 3.6.0.   
Red Hat Enterprise Linux 9 (`rhel9`) is added starting in AWS ParallelCluster version 3.9.0.   
AWS ParallelCluster 3.15 is the last version to include `alinux2` support. Amazon Linux 2 reaches End of Life (EOL) on 2026-06-30 (see [Amazon Linux 2 FAQs ](https://aws.amazon.com/amazon-linux-2/faqs/)) and will no longer receive security patches or bug fixes after EOL. 
All AWS commercial Regions support all of the following operating systems.      
[See the AWS documentation website for more details](http://docs.aws.amazon.com/parallelcluster/latest/ug/Image-v3.html)
[Update policy: If this setting is changed, the update is not allowed.](using-pcluster-update-cluster-v3.md#update-policy-fail-v3)  
 AWS ParallelCluster 3.8.0 supports Rocky Linux 8, but pre-built Rocky Linux 8 AMIs (for x86 and ARM architectures) are not available. AWS ParallelCluster 3.8.0 supports creating clusters with Rocky Linux 8 using custom AMIs. For more information refer to [Operating system considerations](operating-systems-v3.md#OS-Consideration-v3). AWS ParallelCluster 3.9.0 supports Rocky Linux 9, but pre-built Rocky Linux 9 AMIs (for x86 and ARM architectures) are not available. AWS ParallelCluster 3.9.0 supports creating clusters with Rocky Linux 9 using custom AMIs. For more information refer to [Operating System Considerations](operating-systems-v3.md#OS-Consideration-v3).   
 

`CustomAmi` (**Optional**, `String`)  
Specifies the ID of a custom AMI to use for the head and compute nodes instead of the default AMI. For more information, see [AWS ParallelCluster AMI customization](custom-ami-v3.md).  
If the custom AMI requires additional permissions for its launch, these permissions must be added to both the user and head node policies.  
For example, if a custom AMI has an encrypted snapshot associated with it, the following additional policies are required in both the user and head node policies:    
****  

```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "kms:DescribeKey",
                "kms:ReEncrypt*",
                "kms:CreateGrant",
                "kms:Decrypt"
            ],
            "Resource": [
                "arn:aws:kms:{{us-east-1}}:{{111122223333}}:key/{{<AWS_KMS_KEY_ID>}}"
            ]
        }
    ]
}
```
To build a Red Hat Enterprise Linux custom AMI, you must configure the OS for installing the packages that are provided by the RHUI (AWS) repositories: `rhel-<version>-baseos-rhui-rpms`, `rhel-<version>-appstream-rhui-rpms`, and `codeready-builder-for-rhel-<version>-rhui-rpms`. Moreover, the repositories on the custom AMI must contain `kernel-devel` packages on the same version as the running kernel version. kernel.  

**Known limitations:**
+ Only RHEL 8.2 and later versions support FSx for Lustre.
+ RHEL 8.7 kernel version 4.18.0-425.3.1.el8 doesn't support FSx for Lustre.
+ Only RHEL 8.4 and later versions support EFA.
To troubleshoot custom AMI validation warnings, see [Troubleshooting custom AMI issues](troubleshooting-v3-custom-amis.md).  
[Update policy: If this setting is changed, the update is not allowed.](using-pcluster-update-cluster-v3.md#update-policy-fail-v3)