Instances and AMIs - Amazon Elastic Compute Cloud
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Instances and AMIs

An Amazon Machine Image (AMI) is a template that contains a software configuration (for example, an operating system, an application server, and applications). From an AMI, you launch an instance, which is a copy of the AMI running as a virtual server in the cloud. You can launch multiple instances of an AMI, as shown in the following figure.

Launch multiple instances from an AMI.

Your instances keep running until you stop, hibernate, or terminate them, or until they fail. If an instance fails, you can launch a new one from the AMI.


An instance is a virtual server in the cloud. Its configuration at launch is a copy of the AMI that you specified when you launched the instance.

You can launch different types of instances from a single AMI. An instance type essentially determines the hardware of the host computer used for your instance. Each instance type offers different compute and memory capabilities. Select an instance type based on the amount of memory and computing power that you need for the application or software that you plan to run on the instance. For detailed instance type specifications, see Specifications in the Amazon EC2 Instance Types Guide. For pricing information, see Amazon EC2 On-Demand Pricing.

After you launch an instance, it looks like a traditional host, and you can interact with it as you would any computer. You have complete control of your instances; you can use sudo to run commands that require root privileges.

Your Amazon account has a limit on the number of instances that you can have running. For more information about this limit, and how to request an increase, see How many instances can I run in Amazon EC2 in the Amazon EC2 General FAQ.

Storage for your instance

The root device for your instance contains the image used to boot the instance. The root device is either an Amazon Elastic Block Store (Amazon EBS) volume or an instance store volume. For more information, see Amazon EC2 instance root volume.

Your instance may include local storage volumes, known as instance store volumes, which you can configure at launch time with block device mapping. For more information, see Block device mappings. After these volumes have been added to and mapped on your instance, they are available for you to mount and use. If your instance fails, or if your instance is stopped or terminated, the data on these volumes is lost; therefore, these volumes are best used for temporary data. To keep important data safe, you should use a replication strategy across multiple instances, or store your persistent data in Amazon S3 or Amazon EBS volumes. For more information, see Storage options for your Amazon EC2 instances.

Security best practices

  • Use Amazon Identity and Access Management (IAM) to control access to your Amazon resources, including your instances. For more information, see Identity and access management for Amazon EC2.

  • Restrict access by only allowing trusted hosts or networks to access ports on your instance. For example, you can restrict SSH access by restricting incoming traffic on port 22. For more information, see Amazon EC2 security groups for Linux instances.

  • Review the rules in your security groups regularly, and ensure that you apply the principle of least privilege—only open up permissions that you require. You can also create different security groups to deal with instances that have different security requirements. Consider creating a bastion security group that allows external logins, and keep the remainder of your instances in a group that does not allow external logins.

  • Disable password-based logins for instances launched from your AMI. Passwords can be found or cracked, and are a security risk. For more information, see Disable password-based remote logins for the root user. For more information about sharing AMIs safely, see Shared AMIs.

Stop and terminate instances

You can stop or terminate a running instance at any time.

Stop an instance

When an instance is stopped, the instance performs a normal shutdown, and then transitions to a stopped state. All of its Amazon EBS volumes remain attached, and you can start the instance again at a later time.

You are not charged for additional instance usage while the instance is in a stopped state. You are charged for every transition from a stopped state to a running state. If the instance type changed while the instance was stopped, you are charged the rate for the new instance type after the instance is started. You are also charged for the associated Amazon EBS storage for your instance, including the root device volume.

When an instance is in a stopped state, you can attach or detach Amazon EBS volumes. You can also create an AMI from the instance, and you can change the kernel, RAM disk, and instance type.

Terminate an instance

When an instance is terminated, the instance performs a normal shutdown. The root device volume is deleted by default, but any attached Amazon EBS volumes are preserved by default, determined by each volume's deleteOnTermination attribute setting. The instance itself is also deleted, and you can't start the instance again at a later time.

To prevent accidental termination, you can disable instance termination. If you do so, ensure that the disableApiTermination attribute is set to true for the instance. To control the behavior of an instance shutdown, such as shutdown -h in Linux or shutdown in Windows, set the instanceInitiatedShutdownBehavior instance attribute to stop or terminate as desired. Instances with Amazon EBS volumes for the root device default to stop, and instances with instance-store root devices are always terminated as the result of an instance shutdown.

For more information, see Instance lifecycle.


Some Amazon resources, such as Amazon EBS volumes and Elastic IP addresses, incur charges regardless of the instance's state. For more information, see Avoiding Unexpected Charges in the Amazon Billing User Guide. For more information about Amazon EBS costs, see Amazon EBS pricing.


Amazon Web Services (Amazon) publishes Amazon Machine Images (AMIs) that contain common software configurations for public use. In addition, members of the Amazon developer community have published their own custom AMIs. You can also create your own custom AMIs; doing so enables you to quickly and easily start new instances that have everything you need. For example, if your application is a website or a web service, your AMI could include a web server, the associated static content, and the code for the dynamic pages. As a result, after you launch an instance from this AMI, your web server starts, and your application is ready to accept requests.

All AMIs are categorized as either backed by Amazon EBS, which means that the root device for an instance launched from the AMI is an Amazon EBS volume, or backed by instance store, which means that the root device for an instance launched from the AMI is an instance store volume created from a template stored in Amazon S3.

The description of an AMI indicates the type of root device (either ebs or instance store). This is important because there are significant differences in what you can do with each type of AMI. For more information about these differences, see Storage for the root device.

You can deregister an AMI when you have finished using it. After you deregister an AMI, you can't use it to launch new instances. Existing instances launched from the AMI are not affected. Therefore, if you are also finished with the instances launched from these AMIs, you should terminate them.