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AWS Free Tier includes 750 hours of Linux and Windows t2.micro instances each month for one year. To stay within the Free Tier, use only EC2 Micro instances.
AMI - Amazon Machine Instance configurations
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AMIs.html
An Amazon Machine Image (AMI) provides the information required to launch an instance. You must specify an AMI when you launch an instance. You can launch multiple instances from a single AMI when you need multiple instances with the same configuration. You can use different AMIs to launch instances when you need instances with different configurations.
An AMI includes the following:
One or more EBS snapshots, or, for instance-store-backed AMIs, a template for the root volume of the instance (for example, an operating system, an application server, and applications).
Launch permissions that control which AWS accounts can use the AMI to launch instances.
A block device mapping that specifies the volumes to attach to the instance when it's launched.
Linux AMI Virtualization Types
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/virtualization_types.html
Linux Amazon Machine Images use one of two types of virtualization: paravirtual (PV) or hardware virtual machine (HVM). The main differences between PV and HVM AMIs are the way in which they boot and whether they can take advantage of special hardware extensions (CPU, network, and storage) for better performance.
For the best performance, we recommend that you use current generation instance types and HVM AMIs when you launch your instances. For more information about current generation instance types, see Amazon EC2 Instance Types. If you are using previous generation instance types and would like to upgrade, see Upgrade Paths.
HVM AMIs
HVM AMIs are presented with a fully virtualized set of hardware and boot by executing the master boot record of the root block device of your image. This virtualization type provides the ability to run an operating system directly on top of a virtual machine without any modification, as if it were run on the bare-metal hardware. The Amazon EC2 host system emulates some or all of the underlying hardware that is presented to the guest.
Unlike PV guests, HVM guests can take advantage of hardware extensions that provide fast access to the underlying hardware on the host system. For more information on CPU virtualization extensions available in Amazon EC2, see Intel Virtualization Technology on the Intel website. HVM AMIs are required to take advantage of enhanced networking and GPU processing. In order to pass through instructions to specialized network and GPU devices, the OS needs to be able to have access to the native hardware platform; HVM virtualization provides this access. For more information, see Enhanced Networking on Linux and Linux Accelerated Computing Instances.
All instance types support HVM AMIs.
To find an HVM AMI, verify that the virtualization type of the AMI is set to hvm, using the console or the describe-images command.
EBS - Elastic Block Storage devices
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