AMI - Amazon Machine Images

AMI - Amazon Machine Image is Operating system image which AWS understands.

AMI provides good use case in AWS world. For example:
You can make AMI template - Loaded with OS, Libraries, Applications etc.
We can deploy it to 100 instances!

Example for an AMI, a web developer can do the following steps:
1. Configure Operating System.
2. Configure Web Server.
3. Configure PHP, MySQL etc.
4. Make AMI template and save it.

You can install web server in a Linux AMI via the following command.
# yum install httpd -d
# cd /var/www/html

Mount the data partition to /var/www/html via the following command.
# mount /dev/xvdb1 /var/www/html

Install PHP via the following command.
# yum install php

AMI created is region specific.
If you want your AMI available in another region like Chicago, we have to create public AMI.
Alternatively, you can use Copy AMI feature. Recently Amazon launched this feature.