EC2 provides virtual servers in AWS.

Instance

An EC2 instance is a virtual machine.

You choose:

• AMI.
• Instance type.
• Storage.
• Network.
• Security group.
• Key pair or access method.

EC2 gives flexibility, but you manage more than with fully managed services.

AMI

An AMI is an Amazon Machine Image. It is the starting template for an instance.

It includes:

• Operating system.
• Preinstalled software.
• Configuration.

Common AMIs include Amazon Linux, Ubuntu, and Windows Server.

Instance types

Instance types define CPU, memory, networking, and hardware characteristics.

Examples:

• General purpose.
• Compute optimized.
• Memory optimized.
• Storage optimized.

Pick based on workload, not guesswork.

Security groups

Security groups control inbound and outbound traffic.

For a backend server:

• Avoid exposing SSH to the whole internet.
• Allow app traffic only from a load balancer.
• Allow database traffic only to the database port.

User data

User data runs scripts when an instance starts.

It is often used to:

• Install packages.
• Pull application code.
• Start services.
• Configure agents.

Do not put secrets directly in user data.

Operational responsibility

With EC2, you usually own:

• OS updates.
• Runtime installation.
• Disk management.
• Process supervision.
• Security hardening.
• Monitoring agent setup.

Quick revision

• EC2 is virtual servers.
• AMI is the server image.
• Instance type controls capacity.
• Security groups are critical.
• EC2 gives control but requires operational work.