There is a solution. It lies in the –block-device-mappings parameter that can be passed to aws ec2 run-instances command.

According to the documentation this parameter uses JSON-encoded block device mapping to adjust different parameter of the instances that are being started. There is a simple example that shows how to attach additional volume:

--block-device-mappings "[{\"DeviceName\": \"/dev/sdh\",\"Ebs\":{\"VolumeSize\":100}}]"

This will attach additional 100GB EBS volume as /dev/sdb. The key part: “Ebs”: {“VolumeSize”: 100}

By specifying your instance’s root partition you can adjust the root partition size. Following is an example how to create Amazon Linux instance running on t1.micro with 32GB root partition:

aws ec2 run-instances --image-id ami-fb8e9292 --count 1 --instance-type t1.micro --key-name test-key --security-groups test-sg --block-device-mapping "[ { \"DeviceName\": \"/dev/sda1\", \"Ebs\": { \"VolumeSize\": 32 } } ]"

The resulting volume details show the requested size and the fact that this is indeed root partition:

Confirming, that the instance is operating on the proper volume:

:~> ssh ec2-user@ec2-50-16-57-145.compute-1.amazonaws.com "df -h"
Filesystem      Size  Used Avail Use% Mounted on
/dev/xvda1       32G  1.1G   31G   4% /
devtmpfs        282M   12K  282M   1% /dev
tmpfs           297M     0  297M   0% /dev/shm
:~>

There is enough space in the root partition now. Note: This is EBS volume, additional charges will apply!

References

• aws ec2 run-instances help