StartInstances, StopInstances, RebootInstances

Objective

Three actions that change whether an instance is running. They differ in what survives, what is charged, and whether the instance may move to another machine.

Permissions

Action	Resource scope	ARN shape
ec2:StartInstances	Resource-scoped	instance/<id>
ec2:StopInstances	Resource-scoped	instance/<id>
ec2:RebootInstances	Resource-scoped	instance/<id>

Instructions

StopInstances

Shuts the operating system down and releases CPU and memory. The root volume is kept.

Parameter	Type	Required	Notes
InstanceId.N	list	Yes
Force	boolean	No	Stop without a clean shutdown
DryRun	boolean	No

Force skips the guest shutdown. It is the equivalent of removing power, and it risks filesystem corruption in the same way. Use it when a guest has stopped responding, not as a default.

Response: instancesSet, each with instanceId, previousState and currentState.

<StopInstancesResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
  <requestId>b1e2c3d4-5678-90ab-cdef-1234567890ab</requestId>
  <instancesSet>
    <item>
      <instanceId>i-0a1b2c3d4e5f60718</instanceId>
      <currentState><code>64</code><name>stopping</name></currentState>
      <previousState><code>16</code><name>running</name></previousState>
    </item>
  </instancesSet>
</StopInstancesResponse>

Billing: rating counts a running instance, by its shape, per hour — so the charge ends when the instance leaves running.

Its root disk is not billed separately, because storage is not rated at all today. It does still occupy the pool, so a stopped instance costs you nothing and costs the platform capacity. See Billing user guide.

The public address is not retained. A stopped instance that is started again may receive a different address.

Stopping an already-stopped instance succeeds and reports its current state.

StartInstances

Starts a stopped instance.

Parameter	Type	Required
InstanceId.N	list	Yes
DryRun	boolean	No

The instance returns to pending, then running. It may be placed on a different physical machine, which is why a start can fail for capacity when the original launch did not.

Errors

Code	Status	Cause
IncorrectInstanceState	400	The instance is not stopped
InsufficientInstanceCapacity	500	No capacity for that type now
InvalidInstanceID.NotFound	400	No such instance

InsufficientInstanceCapacity on a start is worth calling out: an instance you stopped is not capacity held for you. Stopping releases it, and starting competes for it again.

RebootInstances

Restarts the guest operating system in place.

Parameter	Type	Required
InstanceId.N	list	Yes
DryRun	boolean	No

The instance does not leave running, does not change machine, keeps its address, and continues to be charged. The response carries no instance state, only a request id and return.

A reboot is not a stop-then-start, and cannot be used to move an instance to a different machine or to change its address.

Which to use

You want to	Use
Restart the OS	RebootInstances
Stop paying for compute, keep the disk	StopInstances
Stop paying entirely, lose the disk	TerminateInstances
Move to another machine	Stop, then start

Go further

• TerminateInstances
• Instance lifecycle