amazon-web-services aws - What data is stored in Ephemeral Storage of Amazon EC2 instance?




any lost. (5)

I am trying to stop a Amazon EC2 instance and get the warning message

Warning: Please note that any data on the ephemeral storage of your instance will be lost when it is stopped.

My Question

What data is stored in ephemeral storage of an Amazon EC2 instance?


Answers

Basically, root volume (your entire virtual system disk) is ephemeral, but only if you choose to create AMI backed by Amazon EC2 instance store.

If you choose to create AMI backed by EBS then your root volume is backed by EBS and everything you have on your root volume will be saved between reboots.

If you are not sure what type of volume you have, look under EC2->Elastic Block Store->Volumes in your AWS console and if your AMI root volume is listed there then you are safe. Also, if you go to EC2->Instances and then look under column "Root device type" of your instance and if it says "ebs", then you don't have to worry about data on your root device.

More details here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/RootDeviceStorage.html


To be clear and answer @Dean's question: EBS-type root storage doesn't seem to be ephemeral. Data is persistent across reboots and actually it doesn't make any sense to use ebs-backed root volume which is 'ephemeral'. This wouldn't be different from image-based root volume.


Anything that is not stored on an EBS volume that is mounted to the instance will be lost.

For example, if you mount your EBS volume at /mystuff, then anything not in /mystuff will be lost. If you don't mount an ebs volume and save stuff on it, then I believe everything will be lost.

You can create an AMI from your current machine state, which will contain everything in your ephemeral storage. Then, when you launch a new instance based on that AMI it will contain everything as it is now.

Update: to clarify based on comments by mattgmg1990 and glenn bech:

Note that there is a difference between "stop" and "terminate". If you "stop" an instance that is backed by EBS then the information on the root volume will still be in the same state when you "start" the machine again. According to the documentation, "By default, the root device volume and the other Amazon EBS volumes attached when you launch an Amazon EBS-backed instance are automatically deleted when the instance terminates" but you can modify that via configuration.


According to AWS documentation [https://aws.amazon.com/premiumsupport/knowledge-center/instance-store-vs-ebs/] instance store volumes is not persistent through instance stops, terminations, or hardware failures. Any AMI created from instance stored disk doesn't contain data present in instance store so all instances launched by this AMI will not have data stored in instance store. Instance store can be used as cache for applications running on instance, for all persistent data you should use EBS.


Well, looking at your post description I feel there were 2 mistakes done by you:-

  1. Set correct permissions for the private key. Below command should help you to set correct file permision.

    chmod 0600 mykey.pem

  2. Wrong ec2 user you are trying to login.

    Looking at your debug log I think you have spawned an Amazon linux instance. The default user for that instance type is ec2-user . If the instance would have been ubuntu then your default user would have been ubuntu .

    ssh -i privatekey.pem [email protected]_ip

Note:
   For an Amazon Linux AMI, the default user name is ec2-user.

   For a Centos AMI, the default user name is centos.

   For a Debian AMI, the default user name is admin or root.

   For a Fedora AMI, the default user name is ec2-user or fedora.

   For a RHEL AMI, the default user name is ec2-user or root.

   For a SUSE AMI, the default user name is ec2-user or root.

   For an Ubuntu AMI, the default user name is ubuntu.

   Otherwise, if ec2-user and root don't work, check with the AMI provider.

source: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AccessingInstancesLinux.html





amazon-web-services amazon-ec2 amazon-ebs