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EBS DeleteOnTermination

Here’s how to set the DeleteOnTermination setting on EBS volumes. The DeleteOnTermination flag determines if an EBS volume will be kept or deleted when an EC2 instance is terminated. The DeleteOnTermination setting can be set during EC2 instance creation, or it can be applied to an existing or a running EC2 instance. The settings can be placed in a JSON file and loaded using –block-device-mappings option upon creation.

During creation.

aws ec2 run-instances \
--count 1 \
--region us-east-2 \
--key-name tfc-ohio \
--image-id ami-xxxxxxxx \
--instance-type t2.large \
--subnet-id subnet-xxxxxxx \
--private-ip-address 10.0.4.100 \
--iam-instance-profile Name=machinerole \
--security-group-ids sg-xxxxxxxxxxxxx \
--block-device-mappings file://mapping.json

Contents of mapping.json

[
  {
    "DeviceName": "/dev/sda1",
    "Ebs": {
      "DeleteOnTermination": true,
      "VolumeSize": 30
      "VolumeType": "gp2"
    }
  }
]

Device name is /dev/sda1. Termination is set to true. Volume size is 30GB and EBS type is gp2.

Modifying an existing EC2 instance.

aws ec2 modify-instance-attribute \
--instance-id i-xxxxxxxxxxxxx \
--block-device-mappings file://mapping.json

Here’s the mapping.json file.

[
  {
    "DeviceName": "/dev/sda1",
    "Ebs": {
      "DeleteOnTermination": false,
    }
  }
]

Obviously, you can’t change Volume size and type to an existing EBS volume, but you can flip the DeleteOnTermination flag and vice versa.

AWS Boto3 Client

Boto is the Amazon Web Services (AWS) SDK for Python. It enables Python developers to create, configure, and manage AWS services, such as EC2 and S3. Boto provides an easy to use, object-oriented API, as well as low-level access to AWS services.

Here’s a quick example how to query for AWS resources.

import logging
import boto3
from botocore.exceptions import ClientError
 
# set aws profile
session = boto3.Session(profile_name="default")
 
# get buckets
s3 = session.client('s3')
results = s3.list_buckets()
 
# display buckets
print('Existing buckets:')
for key in results['Buckets']:
    print(f'{key["Name"]}')
 
# get ec2 instances. set region.
ec2 = session.client('ec2', region_name='us-east-1')
results = ec2.describe_instances()
 
# display instances
for key in results["Reservations"]:
      for instance in key["Instances"]:
           instance_id = instance["InstanceId"]
           instance_type = instance["InstanceType"]
           availability_zone = instance["Placement"]["AvailabilityZone"]
           print(instance_id + "\t" + instance_type + "\t" + availability_zone)
 
# get list of users
client = session.client('iam')
results = client.list_users()
 
# display list of users
for key in results['Users']:
    print (key['UserName'])

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.