What is Amazon EC2, and what are the key concepts you need to understand to launch and manage an EC2 instance?

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Amazon Elastic Compute Cloud, or EC2, is the foundational compute service in AWS that provides resizable virtual machines, called instances, in the cloud. EC2 gives you full control over the operating system, installed software, and configuration, making it the most flexible compute option available.

To launch an EC2 instance, you need to understand several key concepts. First is the Amazon Machine Image, or AMI, which is a template containing the operating system and pre-installed software. AWS provides official AMIs for Amazon Linux, Ubuntu, Windows Server, and other operating systems. You can also create custom AMIs from existing instances to capture your specific software configuration, making it easy to launch identical servers.

Second is the instance type, which determines the hardware resources allocated to your virtual machine. Instance types are organized into families based on their optimization. The T family, like t3.micro and t3.medium, provides burstable general-purpose compute suitable for development and light workloads. The M family offers balanced compute, memory, and networking for general-purpose production workloads. The C family is compute-optimized for CPU-intensive tasks. The R family is memory-optimized for databases and caching. Each instance type specifies the number of vCPUs, amount of RAM, network bandwidth, and storage performance.

Third is the key pair, which provides SSH access to Linux instances or decrypts the Windows administrator password. You create a key pair during setup and download the private key file, which must be kept secure because it is the only way to access your instance remotely.

Fourth is the security group, which acts as a virtual firewall controlling inbound and outbound traffic. At minimum, you configure inbound rules for SSH on port 22 from your IP address and any ports your application uses.

Fifth is storage. EC2 instances use Elastic Block Store, or EBS, volumes as their primary storage. You choose the volume type based on performance needs: gp3 for general purpose, io2 for high-performance databases, and st1 for throughput-intensive workloads. Instance store volumes provide temporary storage that is lost when the instance stops.

Sixth is the VPC and subnet placement. You choose which VPC and subnet to launch the instance in, which determines its network connectivity and available IP addresses.

After launching, you connect to the instance via SSH for Linux or RDP for Windows, install your application software, configure services, and manage the instance lifecycle including starting, stopping, rebooting, and terminating. Stopped instances do not incur compute charges but EBS volumes continue to be billed.