Amazon Linux default SSM parameter will now track the latest kernel

Today we are announcing that the Amazon Linux kernel-default AWS Systems Manager (SSM) parameter will now update to point to the latest Amazon Linux kernel version as new kernel versions get released. On August 17, 2026, for Amazon Linux 2023 (AL2023), the SSM parameter was updated from kernel 6.1 to kernel 6.18. As new kernel versions get released (expected annually), the parameter will continue to update to the latest kernel version after a validation period.

This post explains the default kernel behavior, what it means for your workloads, and how to manage the transition.

What’s changing?

Amazon Linux ships multiple kernel versions and has tracked a default kernel for each OS version. For example,
the AL2023 parameter:

ssm:/aws/service/ami-amazon-linux-latest/al2023-ami-{minimal}-kernel-default-{x86_64 arm64}

has remained on kernel 6.1 since launch. Going forward, the kernel-default SSM parameter will update to the latest kernel as new versions are released. Each new kernel will go through a 3- to 6-month validation period after GA before we update the default. This window gives you time to test the new kernel before the change. We will announce the kernel-default upgrade date before it takes effect.

Note: Already-running instances will keep the kernel they booted with and are not affected by this change. Only new instances launched from the kernel-default parameter will boot kernel 6.18. If you already use a version-specific SSM parameter, nothing changes for you.

Why are we making this change?

The Linux kernel is the foundation of workloads you run on Amazon Elastic Compute Cloud (Amazon EC2) and other services. Each new kernel brings meaningful improvements. For example, kernel 6.18 includes the Earliest Eligible Virtual Deadline First (EEVDF) CPU scheduler for fairer CPU time distribution and improved latency in mixed workloads. The kernel also increases Transmission Control Protocol (TCP) receive buffer for better network throughput on high-bandwidth instances.

Previously, customers who wanted to run the latest Amazon Linux kernel had to manually update their SSM parameter references and redeploy each time a new kernel became available. With this change, you can receive these improvements without needing to manually upgrade.

Evaluating the default kernel upgrade

Staying on the default kernel is the recommended approach as it allows your new instances to always run the latest validated kernel with no manual intervention. However, because the default will now advance annually, you should build processes to validate that the new kernel works for your workload before each upgrade takes effect. If your workload has specific requirements that mandate a fixed kernel version, evaluate whether the new default is compatible or revert to a kernel version that suits your use case.

If you haven’t validated kernel 6.18 yet, we recommend launching test instances on kernel 6.18 using the version-specific SSM parameter al2023-ami-{minimal}-kernel-6.18-{x86_64, arm64}. For instructions on referencing SSM parameters in your launch configuration, see the AL2023 User Guide.

Staying on or reverting to a specific kernel version

If you experience issues with the new default, or if your workload requires a specific kernel version for additional validation time or any other reason, revert to the version-specific SSM parameter. Change your references from al2023-ami-{minimal}-kernel-default-x86_64 to al2023-ami-{minimal}-kernel-{kernel_version}-x86_64 (for example, al2023-ami-kernel-6.1-x86_64). This applies anywhere you resolve an AL2023 AMI, including AWS CloudFormation templates, launch templates, Amazon EC2 Auto Scaling groups, CI/CD pipelines, or CLI scripts. For examples, refer to the AL2023 User Guide.

Each of the supported kernels (6.1, 6.12, and 6.18) continue to receive updates as defined in AL2023 kernel lifecycle. When staying on a specific version, we recommend tracking the kernel lifecycle and planning upgrades before the kernel reaches end of support.

Note: For Federal Information Processing Standards (FIPS) workloads, the default kernel may not always be the FIPS-validated kernel. If you require FIPS mode, see AL2023 FIPS FAQ.

Conclusion

In this post, we announced that the Amazon Linux default SSM parameter will now upgrade to the latest kernel as new kernel versions are released. The AL2023 kernel-default parameter was updated from kernel 6.1 to kernel 6.18 on August 17, 2026. We explained how the new cadence works, how already-running instances are unaffected, and how to stay on a specific kernel version if your workload requires it.

To learn more, see the AL2023 Kernel documentation and the AL2023 release notes. For questions or issues, contact AWS Support.