CODEWITHSUNDEEP
amazon-web-servicesamazon-ec2
iCode
iCode

Reputation: 4338

Mount ebs volumes automatically with ebs volume id only

Imagine you have a set of ebs volumes for data and you are frequently mounting these SAME set of EBS volumes to a ec2 node that changes over time (because you kill it every time you do not need it anymore and create a new one when you need it again) but on every creation ec2 instance could have different virtype, OS, instance types an so on (for whatever reason), what is the best way to automatically mount these EBS volumes on this a given ec2 instance when all you have is the ebs volume id and access to ec2 api to get the ebs device name?

Any program available to do so?

Btw, I am not talking about attaching the volumes and interested in automatically mounting to known directories on the os file system on instance creation given that the device name varies from os to os when compared to device name on ec2 and also it is preferred to use UUID in /etc/fstab instead of device name.

Upvotes: 2

Views: 2965

Answers (2)

ambakshi
ambakshi

Reputation: 81

Use filesystem labels:

$ tune2fs -L "disk1" /dev/xvdf
$ tune2fs -L "disk2" /dev/xvdg

In your /etc/fstab:

LABEL=disk1 /disk1 auto defaults 0 2
LABEL=disk2 /disk2 auto defaults 0 2

In you /etc/rc.local:

# Note: You could store the volume-ids and devices in the ec2 tags of your instance.

INSTANCE_ID=$(curl http://169.254.169.254/latest/meta-data/instance-id)
export AWS_DEFAULT_REGION=$(curl http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/[a-z]$//')

aws ec2 attach-volume --volume-id vol-1234abcd --instance-id $INSTANCE_ID --device /dev/xvdf
aws ec2 attach-volume --volume-id vol-1234abcf --instance-id $INSTANCE_ID --device /dev/xvdg

# wait for them to mount
until [ "$(aws ec2 describe-volume-status --volume-id vol-1234abcd --query 'VolumeStatuses[0].VolumeStatus.Status' --output text)" = ok ]; do sleep 5; done

until [ "$(aws ec2 describe-volume-status --volume-id vol-1234abcf --query 'VolumeStatuses[0].VolumeStatus.Status' --output text)" = ok ]; do sleep 5; done

# mount /etc/fstab entries
mount -a

# I also store the EIP as a tag
EIP="$(aws ec2 describe-instances --instance-id $INSTANCE_ID --query 'Reservations[*].Instances[*].[Tags[?Key==`EIP`]|[0].Value]' --output text)"
if [ $? -eq 0 ] && [ "$EIP" != "" ] && [ "$EIP" != "None" ]; then
  aws ec2 associate-address --instance-id $INSTANCE_ID --public-ip "$EIP" --query 'return' --output text
fi

Upvotes: 5

Symfrog
Symfrog

Reputation: 3418

You could script this using AWS CLI and the command attach-volume.

From the AWS CLI example your command would look similar to: 

aws ec2 attach-volume --volume-id vol-1234abcd --instance-id i-abcd1234 --device /dev/sdf

I would also suggest creating an IAM role and attaching it to the ec2 instances that you launch so that you do not have to put any IAM users' credentials on the instance.

You mentioned that you may be attaching the volume to different Operating Systems across ec2 launches, in that case all the OSs would have to support the filesystem type of the partitions on the volume that they wish to mount.

Upvotes: 0

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