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The state of a running EC2 instance can be managed in a number of ways. Terminating the instance will shut it down and cause its resources to be reallocated to the general AWS pool.

Terminating an instance will, in most cases, destroy all data kept on the primary storage. The exception to this would be an Elastic Block Store (EBS) volume that has been set to persist after its instance is terminated.

If your instance won't be needed for some time but you don't want to terminate it, you can save money by simply stopping it and then restarting it when it's needed again. The data on an EBS volume will in this case not be lost, although that would not be true for an instance volume.

Later in this chapter, you'll learn about both EBS and instance store volumes and the ways they work with EC2 instances.

You should be aware that a stopped instance that had been using a nonpersistent public IP address will most likely be assigned a different address when it's restarted. If you need a predictable IP address that can survive restarts, allocate an elastic IP address and associate it with your instance.

You can edit or change an instance's security group (which we'll discuss a bit later in this chapter) to update access policies at any time—even while an instance is running. You can also change its instance type to increase or decrease its compute, memory, and storage capacity (just try doing that on a physical server). You will need to stop the instance, change the type, and then restart it.