Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/aws/exercises/hibernate_instance/exercise.md

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+## AWS EC2 - Hibernate an Instance
+
+### Objectives
+
+1. Create an instance that supports hibernation
+2. Hibernate the instance
+3. Start the instance
+4. What way is there to prove that instance was hibernated from OS perspective?

topics/aws/exercises/hibernate_instance/solution.md

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+## AWS EC2 - Hibernate an Instance
+
+### Objectives
+
+1. Create an instance that supports hibernation
+2. Hibernate the instance
+3. Start the instance
+4. What way is there to prove that instance was hibernated from OS perspective?
+
+### Solution
+
+1. Create an instance that supports hibernation
+  1. Go to EC2 service
+  2. Go to instances and create an instance
+  3. In "Configure instance" make sure to check "Enable hibernation as an additional stop behavior"
+  4. In "Add storage", make sure to encrypt EBS and make sure the size > instance RAM size (because hibernation saves the RAM state)
+  5. Review and Launch
+
+2. Hibernate the instance
+  1. Go to the instance page
+  2. Click on "Instance state" -> "Hibernate instance" -> Hibernate
+
+3. Instance state -> Start
+
+4. Run the "uptime" command, which will display the amount of time the system was up