Amazon EC2

These types can be remembered with…

• D: Density.
• R: RAM.
• M: Main choice for general purpose applications.
• C: Compute.
• G: Graphics.
• I: IOPS.
• F: Field Programmable Gate Array.
• T: "Tiny", cheap general purpose.
• P: Graphics (think Pics)
• X: Extreme memory.

When first creating an EC2 instance you get to choose an Amazon Machine Image (AMI). An AMI is a virtual appliance. The main component is a read-only filesystem image that includes an operating system and any additional software. You can create AMIs from both Volumes and Snapshots.

If you set up an instance, take a snapshot, and then create an AMI, you can use that AMI to launch a new instance that has the same setup. This template can ease future set ups. Note that you cannot delete a snapshot of an EBS Volume that is used as the root device of a registered AMI.

AMIs are regional. You can only launch an AMI from the region in which it is stored. However you can copy AMIs to other regions using the console, command line, or the Amazon EC2 API.

Terminating an instance shuts it down and deletes it. On an EBS-backed instance, the default action is for the root EBS volume to be deleted when the instance is terminated.

You can control whether an EBS root volume is deleted when its associated instance is terminated. The default delete-on-termination behaviour depends on whether the volume is a root volume, or an additional volume. By default, the DeleteOnTermination attribute for root volumes is set to 'true.' However, this attribute may be changed at launch by using either the AWS Console or the command line. For an instance that is already running, the DeleteOnTermination attribute must be changed using the CLI.

Termination Protection can be set on EC2 instances to prevent termination until the option is disabled. Termination Protection is turned off by default.

A Security Group is a virtual firewall. It's a set of rules that control the traffic to and from your instance.

You can have any number of EC2 instances within a Security Group. You can also have multiple Security Groups attached to EC2 instances.

Changes to Security Groups take effect immediately.

You can ssh into an EC2 instance with

#+BEGIN_SRC sh ssh ec2-user@<public-ip> -i keyPair.pem #+END_ARC

Manually setting credentials with aws configure can be a security risk on EC2 instances. If an EC2 instance is compromised, these credentials can be stolen. In addition, setting credentials in this way can be difficult to manage. Roles can improve security and ease management. Create a role using IAM. Roles can be attached to EC2 instances when they are created or even when they are running.

You can change the permissions to a role, even if that role is already assigned to an existing EC2 instance, and these changes will take effect immediately.

When you launch an instance in Amazon EC2, you can choose to run user data. This may be a shell script. Specify a script under Advanced Details during the launch wizard. Use a shebang (#!) at the start of the script. You can see the contents of user data with curl http://169.254.169.254/latest/user-data/.

Retrieve metadata about your current EC2 instance with curl http://169.254.169.254/latest/meta-data/. This will give a list of variables. To get the public IP address, run curl http://169.254.169.254/latest/meta-data/public-ipv4.

An Auto Scaling group contains a collection of EC2 instances that share similar characteristics and are treated as a logical group for the purposes of instance scaling and management. For example, if a single application operates across multiple instances, you might want to increase the number of instances in that group to improve the performance of the application, or decrease the number of instances to reduce costs when demand is low. You can use the Auto Scaling group to scale the number of instances automatically based on criteria that you specify, or maintain a fixed number of instances even if an instance becomes unhealthy.

Create an Auto Scaling group through the EC2 page on the AWS console. First you'll need to create a launch configuration. Creating this template looks very similar to a normal EC2 launch. Next, create an Auto Scaling group. Specify how many instances you want to run in the group. Your group will maintain this number of instances, and replace any that become unhealthy or impaired. You can optionally configure your group to adjust in capacity according to demand, in response to Amazon CloudWatch metrics.

A Placement Group is a logical grouping of instances within a single Availability Zone. Using placement groups enables applications to participate in a low-latency, 10 Gbps network. Placement groups are recommended for applications that benefit from low network latency, high network throughput, or both.

• A placement group can't span multiple Availability Zones (make sense, we're looking for high network speed).
• The name you specify for a placement group must be unique within your AWS account.
• Only certain types of instances can be launched in a placement group (Compute Optimized, GPU, Memory Optimized, Storage Optimized).
• AWS recommend homogenous instances within placement groups.
• You can't merge placement groups.
• You can't move an existing instance into a placement group. You can create an AMI from your existing instance, and then launch a new instance from the AMI into a placement group.