Upgrade EC2 Instance RAM is not updated

When you upgrade an EC2 instance type, such as from c3 to r5, the change in RAM is not automatically reflected in the operating system. The instance type change only affects the underlying hardware resources available to the instance. To make the additional RAM visible and usable within your SuSE Linux Enterprise 15 SP5 operating system, you need to take a few additional steps:

1. First, verify that your instance is indeed running on the new r5 instance type by checking the instance details in the EC2 console or using AWS CLI commands.

2. If the instance type has been successfully changed, you'll need to stop and start the instance (not just reboot) for the new hardware configuration to be fully recognized by the operating system.

3. After the instance has been stopped and started, connect to it via SSH and use the command 'free -m' or 'top' to check the available memory.

4. If you still don't see the expected 64GB of RAM, you may need to update the kernel or drivers on your SuSE Linux Enterprise 15 SP5 system to fully recognize the new hardware configuration.

5. In some cases, you might need to resize the swap space to match the new RAM size, although this is typically not necessary for the OS to recognize the additional memory.

If after performing these steps you still don't see the expected 64GB of RAM, there might be an issue with the instance type change process or a compatibility problem with your specific OS version. In that case, you should contact AWS support for further assistance.

Remember that changing instance types can sometimes lead to unexpected behavior, especially with older operating systems or custom configurations. It's always a good practice to test such changes in a non-production environment first and to have a backup or snapshot of your instance before making significant changes.
Sources
EBS Storage size not increased after Instance Type upgrade (Linux) | AWS re:Post
EC2 instance memory not available to me | AWS re:Post

Make sure you are using a r5.2xlarge and not a r5.xlarge