Rebooting vs. Stop/Start of Amazon EC2 Instance

| 2 Comments

When you reboot a physical computer at your desk it is very similar to shutting down the system, and booting it back up. With Amazon EC2, rebooting an instance is much the same as with a local physical computer, but a stop/start differs in a few keys ways that may cause some problems and definitely have some benefits.

When you stop an EBS boot instance you are giving up the physical hardware that the server was running on and EC2 is free to start somebody else’s instance there.

Your EBS boot volume (and other attached EBS volumes) are still preserved, though they aren’t really tied to a physical or virtual server. They are just associated with an instance id that isn’t running anywhere.

When you start the instance again, EC2 picks some hardware to run it on, ties in the EBS volume(s) and boots it up again.

Things that change when you stop/start include:

  1. New internal IP address, though could randomly be the same. [VPC instances keep same internal IP addresses through stop/start.]

  2. New external IP address (though could randomly be the same).

  3. If an Elastic IP address was associated with the instance before it was stopped, then you’ll need to re-associate it after the start. [VPC instances keep Elastic IP addresses associated through stop/start.]

  4. Any contents on the instance’s former ephemeral storage were wiped and you are given fresh ephemeral storage (often mounted as /mnt).

  5. You can leave an instance stopped for as long as you like and not get charged for run time (though you do get charged at a much lower rate for the EBS volume storage). See the next point.

  6. A fresh billing hour is started for the instance when you start it again. E.g., if you start a new instance and then stop/start it 3 times within the first 60 minutes, you’ll get charged for 4 hours instead of 1.

  7. There is a small chance that EC2 will not have available slots of the correct instance type to run your instance when you want to start it again. I’ve had this happen and temporarily switched to a different, available instance type to get it running again.

When you reboot, it’s a simple reboot at the OS level and the instance stays running on the same hardware, with the same private and public IP addresses, keeps the same Elastic IP address (if associated), and keeps the same ephemeral storage without getting wiped. No new billing hour is started on a reboot and you do not give up the instance hardware.

While an instance is stopped, you can do some cool things before starting it again. Here’s an article I wrote on changing the instance type of an instance while it’s stopped:

Moving an EC2 Instance to a Larger Size

Here’s an article I wrote on how to change the size of an EBS boot disk of an instance while it’s stopped:

Resizing the Root Disk on a Running EBS Boot EC2 Instance

Here’s an article I wrote on how to examine the root disk of an instance (while it’s stopped) when you can’t connect to it while it’s runnning:

Fixing Files on the Root EBS Volume of an EC2 Instance

Since the stop/start cycle has a good chance of moving your instance to new hardware, it’s an easy way to replace your instance hardware if you suspect that the current platform might be going bad and causing problems. Here’s an article I wrote about that:

A Simpler Way To Replace Instance Hardware on EC2

Warning: “Stopping” an instance is completely different from “terminating” an instance! When you terminate an EC2 instance, by default it deletes the EBS boot volume and other volumes that were created at run time. Make sure you understand the difference before you start doing one or the other.

I originally posted this article as an answer to a serverfault question, but liked it enough to archive it on this blog.

[Update 2013-07-09: Clarified VPC instance behavior thanks to Skaperen on ##aws.]

2 Comments

Steffen Opel notes that a stop/start of an EC2 instance in VPC leaves an Elastic IP address associated. This differs from normal EC2 instance behavior noted above in (3).

Amazon has published a great page that describes in detail what happens when you stop and start an EBS boot instance:

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Stop_Start.html

Leave a comment

Ubuntu AMIs

Ubuntu AMIs for EC2:


More Entries

EC2 create-image Does Not Fully "Stop" The Instance
The EC2 create-image API/command/console action is a convenient trigger to create an AMI from a running (or stopped) EBS boot instance. It takes a snapshot of the instance’s EBS volume(s)…
Finding the Region for an AWS Resource ID
use concurrent AWS command line requests to search the world for your instance, image, volume, snapshot, … Background Amazon EC2 and many other AWS services are divided up into various…
Changing The Default "ubuntu" Username On New EC2 Instances
configure your own ssh username in user-data The official Ubuntu AMIs create a default user with the username ubuntu which is used for the initial ssh access, i.e.: ssh ubuntu@<HOST>…
Default ssh Usernames For Connecting To EC2 Instances
Each AMI publisher on EC2 decides what user (or users) should have ssh access enabled by default and what ssh credentials should allow you to gain access as that user.…
New c3.* Instance Types on Amazon EC2 - Nice!
Worth switching. Amazon shared that the new c3.* instance types have been in high demand on EC2 since they were released. I finally had a minute to take a look…
Query EC2 Account Limits with AWS API
Here’s a useful tip mentioned in one of the sessions at AWS re:Invent this year. There is a little known API call that lets you query some of the EC2…
Using aws-cli --query Option To Simplify Output
My favorite session at AWS re:Invent was James Saryerwinnie’s clear, concise, and informative tour of the aws-cli (command line interface), which according to GitHub logs he is enhancing like crazy.…
Reset S3 Object Timestamp for Bucket Lifecycle Expiration
use aws-cli to extend expiration and restart the delete or archive countdown on objects in an S3 bucket Background S3 buckets allow you to specify lifecycle rules that tell AWS…
Installing aws-cli, the New AWS Command Line Tool
consistent control over more AWS services with aws-cli, a single, powerful command line tool from Amazon Readers of this tech blog know that I am a fan of the power…
Using An AWS CloudFormation Stack To Allow "-" Instead Of "+" In Gmail Email Addresses
Launch a CloudFormation template to set up a stack of AWS resources to fill a simple need: Supporting Gmail addresses with “-” instead of “+” separating the user name from…
New Options In ec2-expire-snapshots v0.11
The ec2-expire-snapshots program can be used to expire EBS snapshots in Amazon EC2 on a regular schedule that you define. It can be used as a companion to ec2-consistent-snapshot or…
Replacing a CloudFront Distribution to "Invalidate" All Objects
I was chatting with Kevin Boyd (aka Beryllium) on the ##aws Freenode IRC channel about the challenge of invalidating a large number of CloudFront objects (35,000) due to a problem…
Email Alerts for AWS Billing Alarms
using CloudWatch and SNS to send yourself email messages when AWS costs accrue past limits you define The Amazon documentation describes how to use the AWS console to monitor your…
Cost of Transitioning S3 Objects to Glacier
how I was surprised by a large AWS charge and how to calculate the break-even point Glacier Archival of S3 Objects Amazon recently introduced a fantastic new feature where S3…
Running Ubuntu on Amazon EC2 in Sydney, Australia
Amazon has announced a new AWS region in Sydney, Australia with the name ap-southeast-2. The official Ubuntu AMI lookup pages (1, 2) don’t seem to be showing the new location…
Save Money by Giving Away Unused Heavy Utilization Reserved Instances
You may be able to save on future EC2 expenses by selling an unused Reserved Instance for less than its true value or even $0.01, provided it is in the…
Installing AWS Command Line Tools from Amazon Downloads
When you need an AWS command line toolset not provided by Ubuntu packages, you can download the tools directly from Amazon and install them locally. In a previous article I…
Convert Running EC2 Instance to EBS-Optimized Instance with Provisioned IOPS EBS Volumes
Amazon just announced two related features for getting super-fast, consistent performance with EBS volumes: (1) Provisioned IOPS EBS volumes, and (2) EBS-Optimized Instances. Starting new instances and EBS volumes with…
Which EC2 Availability Zone is Affected by an Outage?
Did you know that Amazon includes status messages about the health of availability zones in the output of the ec2-describe-availability-zones command, the associated API call, and the AWS console? Right…
Installing AWS Command Line Tools Using Ubuntu Packages
See also: Installing AWS Command Line Tools from Amazon Downloads Here are the steps for installing the AWS command line tools that are currently available as Ubuntu packages. These include:…
Ubuntu Developer Summit, May 2012 (Oakland)
I will be attending the Ubuntu Developer Summit (UDS) next week in Oakland, CA. ┬áThis event brings people from around the world together in one place every six months to…
Uploading Known ssh Host Key in EC2 user-data Script
The ssh protocol uses two different keys to keep you secure: The user ssh key is the one we normally think of. This authenticates us to the remote host, proving…
Seeding Torrents with Amazon S3 and s3cmd on Ubuntu
Amazon Web Services is such a huge, complex service with so many products and features that sometimes very simple but powerful features fall through the cracks when you’re reading the…
CloudCamp
There are a number of CloudCamp events coming up in cities around the world. These are free events, organized around the various concepts, technologies, and services that fall under the…
Use the Same Architecture (64-bit) on All EC2 Instance Types
A few hours ago, Amazon AWS announced that all EC2 instance types can now run 64-bit AMIs. Though t1.micro, m1.small, and c1.medium will continue to also support 32-bit AMIs, it…
ec2-consistent-snapshot on GitHub and v0.43 Released
The source for ec2-conssitent-snapshot has historically been available here: ec2-consistent-snapshot on Launchpad.net using Bazaar For your convenience, it is now also available here: ec2-consistent-snapshot on GitHub using Git You are…
You Should Use EBS Boot Instances on Amazon EC2
EBS boot vs. instance-store If you are just getting started with Amazon EC2, then use EBS boot instances and stop reading this article. Forget that you ever heard about instance-store…
Retrieve Public ssh Key From EC2
A serverfault poster had a problem that I thought was a cool challenge. I had so much fun coming up with this answer, I figured I’d share it here as…
Running EC2 Instances on a Recurring Schedule with Auto Scaling
Do you want to run short jobs on Amazon EC2 on a recurring schedule, but don’t want to pay for an instance running all the time? Would you like to…
AWS Virtual MFA and the Google Authenticator for Android
Amazon just announced that the AWS MFA (multi-factor authentication) now supports virtual or software MFA devices in addition to the physical hardware MFA devices like the one that’s been taking…