What happens when I reboot an EC2 instance?

Question

When I reboot an EC2 instance, do I get the initial image again, or is the state of the hard disk before the reboot kept?

And what happens with billing, does the hour start again, or do I continue with the fraction of the hour I was in when I rebooted?

Simple but very useful question (& answers) - thanks! +1 all around. — Jonik, Apr 16 '10 at 12:38
Agree as rebooted is not the same with restarted an instance after stopped. — eQ19, Jul 18 '16 at 10:13

score 94 · Accepted Answer · answered Mar 12 '09 at 09:26

94

Rebooting an instance is like rebooting a PC. The hard disk isn't affected. You don't return to the image's original state, but the contents of the hard disks are those before the reboot.

Rebooting isn't associated with billing. Billing starts when you instantiate an image and stops when you terminate it. Rebooting in between hasn't any effect.

answered Mar 12 '09 at 09:26

kgiannakakis

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Note that there's a related bug - files in /etc might be changed back to some defaults (Google it). – Adam Matan Aug 06 '09 at 14:50
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@AdamMatan link? I have a problem with losing `/etc/resolv.conf` on reboot. – Petrus Theron Jun 17 '13 at 13:11
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Just to make it clear: You are not charged for stopped instances (besides the EBS volumes). EC2 instances only cost you when they're running. – Philippe Gerber Jul 21 '13 at 16:58
Yes there will be charge by the volumes but [EBS is charged hourly](http://serverfault.com/a/197578/366042) – eQ19 Jul 20 '16 at 05:19

score 24 · Answer 2 · answered Mar 12 '09 at 09:29

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Rebooting keeps the disks intact.

If you shut down the instance and power up a new one, the disks will be reset to their initial states.

This doesn't apply to the EBS disks, which persist even across shutdowns.

answered Mar 12 '09 at 09:29

Barry Brown

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> if you shut down the instance and power up a new one, the disks will be reset to their initial states. this answer directly contradicts the top answer – swyx Feb 09 '20 at 21:52

score 19 · Answer 3 · answered Apr 09 '17 at 13:33

As per AWS Documentation:

An instance reboot is equivalent to an operating system reboot. In most cases, it takes only a few minutes to reboot your instance. When you reboot an instance, it remains on the same physical host, so your instance keeps its public DNS name (IPv4), private IPv4 address, IPv6 address (if applicable), and any data on its instance store volumes.

Rebooting an instance doesn't start a new instance billing hour, unlike stopping and restarting your instance.

Further, they recommend:

We recommend that you use Amazon EC2 to reboot your instance instead of running the operating system reboot command from your instance. If you use Amazon EC2 to reboot your instance, we perform a hard reboot if the instance does not cleanly shut down within four minutes.

The latest docs say "within a few minutes" I want a hard reboot to reboot *now*. I also don't want to wait 10s for it to decide to boot. Grr. — timkay, Aug 05 '22 at 17:37

score 1 · Answer 4 · answered Jun 01 '16 at 21:01

When you rebooting an instance, it will keep remains same hypervisor and restart the VM just like normal Linux reboot.

If you created a VM with ephemeral block store, then you would not lose the ephemeral storage when you restart the instance.

As mentioned above, rebooting will not affect the billing

score 0 · Answer 5 · answered Sep 06 '21 at 18:05

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go to instance and reboot. I just did and all my states and the data were intact. Wait for a few minutes before everything comes back to normal.

answered Sep 06 '21 at 18:05

jacai

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What happens when I reboot an EC2 instance?

5 Answers5

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