31 Jul 2013

AWS: Attaching an EBS volume on an EC2 instance and making it available for use

I recently wanted to attach an EBS volume to an existing EC2 instance that I had running and since it was for a one off tasks (famous last words) I decided to configure it manually.

I created the EBS volume through the AWS console and one thing that initially caught me out is that the EC2 instance and EBS volume need to be in the same region and zone.

Therefore if I create my EC2 instance in 'eu-west-1b' then I need to create my EBS volume in 'eu-west-1b' as well otherwise I won’t be able to attach it to that instance.

I attached the device as /dev/sdf although the UI gives the following warning:

Linux Devices: /dev/sdf through /dev/sdp Note: Newer linux kernels may rename your devices to /dev/xvdf through /dev/xvdp internally, even when the device name entered here (and shown in the details) is /dev/sdf through /dev/sdp.

After attaching the EBS volume to the EC2 instance my next step was to SSH onto my EC2 instance and make the EBS volume available.

The first step is to create a file system on the volume:

$ sudo mkfs -t ext3 /dev/sdf
mke2fs 1.42 (29-Nov-2011)
Could not stat /dev/sdf --- No such file or directory

The device apparently does not exist; did you specify it correctly?

It turns out that warning was handy and the device has in fact been renamed. We can confirm this by calling fdisk:

$ sudo fdisk -l

Disk /dev/xvda1: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/xvda1 doesn't contain a valid partition table

Disk /dev/xvdf: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders, total 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/xvdf doesn't contain a valid partition table

/dev/xvdf is the one we’re interested in so I re-ran the previous command:

$ sudo mkfs -t ext3 /dev/xvdf
mke2fs 1.42 (29-Nov-2011)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
3276800 inodes, 13107200 blocks
655360 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
400 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
	4096000, 7962624, 11239424

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

Once I’d done that I needed to create a mount point for the volume and I thought the best place was probably a directory under /mnt:

$ sudo mkdir /mnt/ebs

The final step is to mount the volume:

$ sudo mount /dev/xvdf /mnt/ebs

And if we run df we can see that it’s ready to go:

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/xvda1      7.9G  883M  6.7G  12% /
udev            288M  8.0K  288M   1% /dev
tmpfs           119M  164K  118M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            296M     0  296M   0% /run/shm
/dev/xvdf        50G  180M   47G   1% /mnt/ebs

About the author

I'm currently working on short form content at ClickHouse. I publish short 5 minute videos showing how to solve data problems on YouTube @LearnDataWithMark. I previously worked on graph analytics at Neo4j, where I also co-authored the O'Reilly Graph Algorithms Book with Amy Hodler.