When you fire up an AWS AMI, you are given a small partition of disk space that survives reboots. For example, the base Ubuntu AMI I tend to favor comes with an 8GB primary partition; however, 8GB is often not enough, especially if you’re running a database or something that requires a lot of disk space.
If you poke around on an AMI instance, you’ll notice some AMI instances will have additional partitions and in many cases, these partitions will be huge; nevertheless, they’re transient and any data on those disks will disappear after a reboot.
Accordingly, if you need to gain some more permanent space on an AMI instance, you’ll need to leverage an Elastic Block Store (or EBS), which is basically a permanent hard disk that you can attach to a running AMI instance. The data on an EBS will survive a reboot.
Attaching an EBS is super simple and can be done in 4 steps. These steps assume you’ve got a running AMI; accordingly, if you don’t have one up and running, go ahead and do that first. Finally, these instructions are for Linix/Unix systems.
First, you’ll need to create an EBS volume in the same zone as the AMI instance. In my case, the instance I’d like to augment with a beefy hard drive resides in us-east-1b. What’s more, you’ll need to configure how much space you’ll want – you can also select if you’d like to have provisioned IOPS – this is a high performance I/O feature of AWS and is intended for databases.
Once the EBS is created, you’ll need to attach it to your running AMI – you can do this by right clicking on the EBS in the AWS Management Console and selecting Attach Volume. You’ll need to pick your instance from a drop down. Once you’ve picked your instance, AWS will suggest a Device – I suggest you keep it. Click the “Yes, Attach” button.
SSH onto your running instance and take a peek at the
/proc/partitions file – you should see at least 2 partitions with your newly attached one on the bottom. The blocks are listed in kilobytes and pay special attention to the name – you’ll need it for the next few steps.
As you can see above, there is an 8GB EBS volume named
xvdf in the
Next, you’ll want to format the volume – I’m going to format the EBS volume as ext4. The command to do this is:
Now that the volume is formatted, I can mount it – I’m going to mount it to a directory called
/ebs; accordingly, I need to create the
/ebs directory and then mount the
xvdf device like so:
At this point, you are 98% done; however, the volume will not be reattached if this instance is rebooted.
To make this EBS volume automatically reattach after a reboot, you’ll need to add it to the
fstab file (it’s in the
/etc directory). When you edit that file, the file system will be
what ever you mounted (i.e
/dev/xvdf), the mount point will be the directory you mounted it to – in my case, it’s
/ebs. The type will be ext4 (if you formatted it that way) and for options, put default. The last two values can be 0 as well.
If you need to remove your EBS volume, on the attached instance, run
And then go into the AWS Management Console, find your EBS volume, right click on it and select detach volume.
That’s it – you’re done! You’ve got a permanent store. In 4 steps, you’ve created an EBS volume, attached it to a running AMI, formatted and mounted it. And you’ve made it attach automatically after a reboot. Can you dig it?