Is it "safe" to create a AMI image from a running EBS instance with another EBS attached to it?

Question

I have an EBS backed AMI up and running and another EBS attached and mounted as a persistant storage device. Is it safe for me to create an a new AMI image (via the AWS Management UI) while the storage block is attached?

Answer 1

It should be safe in terms of "doesn't crash". You might need to consider the following though:

• Do you want to exclude the path where the other EBS volume is mounted?
• Do you have enough space left to do so?

Apart from that, it's like having any other file system attached (e.g. network file systems). Unless you explicitly add them to the startup configuration (e.g. /etc/fstab), it won't be a problem.

Answer 2

It’s “safe” if you do it at a time when it’s safe for the machine to be restarted, but it’s not a good idea because the AMI will include the ‘other EBS’. That ‘other EBS’ will be recreated for each new instance you launch from that AMI. The problem with that is that it is never deleted! The instance’s system volume is (by default) automatically deleted when the instance is terminated – but not any attached EBS volumes! You end up with an orphaned EBS volumes for each instance of an AMI created in this way.

You want that attached drive for persistent storage, not to be recreated anew each time. Detach it, make a snapshot of it for it’s protection if appropriate, then make your AMI while it is detached. After you launch an instance from your new AMI, reattach the EBS volume you use for persistent storage.