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Amazon Elastic Compute Cloud (EC2) is the backbone of AWS compute. It lets you launch virtual servers — called instances — in minutes, scale capacity up or down on demand, and pay only for what you use. Whether you need a single development box or thousands of production servers, EC2 provides the building blocks.
EC2 is an Infrastructure as a Service (IaaS) offering. You get full control over the operating system, networking, and storage of every instance you launch. AWS manages the physical hardware, hypervisor, and data-centre facilities; you manage everything from the guest OS upward.
Think of EC2 as renting a computer in the cloud. You choose:
Once the instance is running, you can SSH or RDP into it just like a physical machine.
Before EC2, provisioning a new server could take weeks — procurement, racking, cabling, OS installation, and configuration. EC2 reduces that to minutes or seconds. This speed unlocks several benefits:
| Benefit | Description |
|---|---|
| Elasticity | Scale from one instance to thousands, then back down |
| Cost efficiency | Pay per second (Linux) or per hour (Windows), with no long-term commitment required |
| Global reach | Launch instances in any AWS Region or Availability Zone |
| Variety | 750+ instance types optimised for different workloads |
| Integration | Tight integration with other AWS services (S3, RDS, IAM, CloudWatch, etc.) |
| Reliability | Built on AWS's proven global infrastructure with multiple levels of redundancy |
An EC2 instance is a virtual server. Each instance runs on a physical host managed by AWS and is isolated from other instances using the Nitro Hypervisor (or the older Xen hypervisor for legacy instance types).
An AMI is a template that contains the operating system, application server, and applications. You select an AMI when you launch an instance. AWS provides thousands of public AMIs, and you can create your own custom AMIs.
Instance types determine the hardware profile — how many vCPUs, how much RAM, what storage is available, and how much network bandwidth the instance receives. Instance types are grouped into families (e.g., General Purpose, Compute Optimised, Memory Optimised).
AWS operates in multiple Regions around the world (e.g., us-east-1, eu-west-2). Each Region contains multiple Availability Zones (AZs) — physically separate data centres with independent power, cooling, and networking. Spreading instances across AZs improves fault tolerance.
AWS uses public-key cryptography to secure login to instances. You create a key pair; AWS stores the public key on the instance, and you keep the private key. For Linux instances, you use the private key with SSH; for Windows, you decrypt the administrator password.
A security group acts as a virtual firewall controlling inbound and outbound traffic to your instance. By default, all inbound traffic is denied and all outbound traffic is allowed. You add rules to permit specific protocols, ports, and source IP ranges.
The simplest way to launch an instance is through the AWS Management Console:
t2.micro is free-tier eligible (1 vCPU, 1 GiB RAM).After a few seconds the instance enters the running state and you receive a public IP address (if enabled).
# Make your private key read-only
chmod 400 my-key-pair.pem
# Connect to the instance
ssh -i my-key-pair.pem ec2-user@<public-ip>
Replace ec2-user with the appropriate default user for your AMI (ubuntu for Ubuntu, Administrator for Windows via RDP).
Every EC2 instance moves through a series of states:
pending → running → stopping → stopped → terminated
↘ shutting-down → terminated
↗ rebooting → running
| State | Description | Billing? |
|---|---|---|
| pending | Instance is being prepared | No |
| running | Instance is active and reachable | Yes |
| stopping | Instance is in the process of stopping | Depends on instance store |
| stopped | Instance is shut down; EBS volumes persist | No (but EBS charges apply) |
| shutting-down | Instance is being terminated | No |
| terminated | Instance is deleted; cannot be restarted | No |
| rebooting | Instance is rebooting; stays in "running" | Yes |
Key points:
DeleteOnTermination attribute.While the console is great for exploration, most production workflows use the AWS CLI or SDKs. Here are common EC2 commands:
# List running instances
aws ec2 describe-instances --filters "Name=instance-state-name,Values=running"
# Launch an instance
aws ec2 run-instances \
--image-id ami-0abcdef1234567890 \
--instance-type t3.micro \
--key-name my-key-pair \
--security-group-ids sg-0123456789abcdef0 \
--subnet-id subnet-0bb1c79de3EXAMPLE
# Stop an instance
aws ec2 stop-instances --instance-ids i-0123456789abcdef0
# Terminate an instance
aws ec2 terminate-instances --instance-ids i-0123456789abcdef0
Understanding what you manage versus what AWS manages is critical:
| Your Responsibility | AWS Responsibility |
|---|---|
| Guest OS patches and updates | Physical host hardware |
| Application software | Hypervisor and firmware |
| Security group rules | Data-centre security |
| Data encryption | Network infrastructure |
| IAM policies and access control | Power, cooling, environmental controls |
Amazon EC2 is the foundation of compute on AWS. It provides virtual servers with full OS-level control, a rich set of instance types, and seamless integration with the broader AWS ecosystem. Understanding how to launch, connect to, manage, and terminate instances — along with the shared responsibility model — is the first step toward building scalable, reliable infrastructure in the cloud.