Core comparison
| Operation | RAM and processes | EBS | Instance store | Start again? |
|---|---|---|---|---|
| Reboot | The OS restarts | Retained | Usually retained | Returns to Running |
| Stop | Cleared | Retained | Lost | Yes |
| Hibernate | RAM is written to the encrypted root EBS volume and later restored | Retained | Lost | Yes |
| Terminate | Cleared | Controlled by Delete on Termination | Lost | No |
Hibernation must be enabled at launch and requires a supported AMI, OS, and instance type plus an encrypted root EBS volume with enough capacity.
Boundaries
- Hibernation preserves runtime state; it is not backup, snapshot, DR, or Multi-AZ HA.
- Compute charges stop after stop/hibernate, but EBS and public IPv4 resources can still cost money.
- The primary private IPv4 normally remains; an auto-assigned public IPv4 is usually released; an Elastic IP stays associated.
- A later start does not normally rerun first-boot user data.
- Volume deletion on termination depends on the block device mapping.
Decision cues
Preserve RAM and processes → Hibernate; ordinary shutdown → Stop; restart only the OS → Reboot; permanently remove the instance → Terminate.
Remember
Stop keeps disks but not memory; Hibernate stores memory on encrypted root EBS; Terminate is irreversible.