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cloud engineer

AWS EC2 ENA Support

AWS has machine types that require ENA Support. You can run AWS CLI to find out if instance is ENA enabled.

aws ec2 describe-instances \
--instance-id i-xxxxxxxxxxxxxxxxx \
--profile default \
--region us-east-1 \
--query 'Reservations[].Instances[].EnaSupport'

Login to the instance and verify.

sudo lspci | grep -i Amazon

List driver details.

modinfo nvme

Verify modules loaded at startup.

lsmod | grep nvme
lsmod | grep ena

If ENA drivers are missing, install them.

yum install pciutils

AWS Enable Enhance Network Support

When changing machine types, you may be asked to enable the latest ENA driver for Enhanced Network Support on an Amazon EC2 instance. There are several instructions depending on the Linux OS flavor. Here are the instructions to enable. In some cases, you may need to rebuild the kernel module. To verify that the ena module is installed, use the modinfo command as shown in the following example.

modinfo ena

You also may have to enable the enhanced networking attribute on the instance.

aws ec2 modify-instance-attribute --instance-id instance_id --ena-support

AWS Instance Type to M5 or C5

If you have changed instance type to either C5 or M5 and it no longer boots, it’s due to the following reasons.

  1. The Elastic Network Adapter (ENA) enaSupport attribute is disabled for the instance.
  2. The ENA module isn’t installed on the instance
  3. The NVMe module isn’t installed on the instance, or, if installed, the NVMe module isn’t loaded in the initramfs image of the instance.
  4. You are trying to mount the file systems at boot time in the “/etc/fstab” file using a device name. Amazon Elastic Block Store (Amazon EBS) volumes are exposed as NVMe devices to these instance types, and the device names are changed. To avoid this, mount the file systems using UUID/Label. For more information, see Amazon EBS and NVMe.

You will need to run a Bash script to update the current instance to be able to support a C5 or M5 instance.