Expanding root partition on AWS-ECS Docker contianer - amazon-web-services

Question

How do I expand the root partition of all containers of a certain task definition by default? If it expands all containers in an instance or cluster (including the ECS Agent), that's still fine.
After reading https://docs.aws.amazon.com/AmazonECS/latest/developerguide/bootstrap_container_instance.html, I tried adding
#cloud-boothook
cloud-init-per once docker_options echo 'OPTIONS="${OPTIONS} --storage-opt dm.basesize=25G"' >> /etc/sysconfig/docker to the autoscaling group's advanced details, but to no avail.
I also tried (with no success) all of the following (in the same place):
sed -i '/^EXTRA_DOCKER_STORAGE_OPTIONS/s/"$/ --storage-opt dm.basesize=25G"/' /etc/sysconfig/docker-storage-setup
sed -i '/^DOCKER_STORAGE_OPTIONS/s/"$/ --storage-opt dm.basesize=25G"/' /etc/sysconfig/docker-storage
and
sed -i '/^OPTIONS/s/"$/ --storage-opt dm.basesize=25G"/' /etc/sysconfig/docker
None of them worked.
I tried updating the ECS-Agent from 1.18 to 1.23.
These solutions failed on both versions.
docker info output:
Containers: 2
Running: 2
Paused: 0
Stopped: 0
Images: 3
Server Version: 18.06.1-ce
Storage Driver: devicemapper
Pool Name: docker-docker--pool
Pool Blocksize: 524.3kB
Base Device Size: 10.74GB
Backing Filesystem: ext4
Udev Sync Supported: true
Data Space Used: 4.298GB
Data Space Total: 106.1GB
Data Space Available: 101.8GB
Metadata Space Used: 708.6kB
Metadata Space Total: 109.1MB
Metadata Space Available: 108.3MB
Thin Pool Minimum Free Space: 10.61GB
Deferred Removal Enabled: true
Deferred Deletion Enabled: true
Deferred Deleted Device Count: 0
Library Version: 1.02.135-RHEL7 (2016-11-16)
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 468a545b9edcd5932818eb9de8e72413e616e86e
runc version: 69663f0bd4b60df09991c08812a60108003fa340
init version: fec3683
Security Options:
seccomp
Profile: default
Kernel Version: 4.14.67-66.56.amzn1.x86_64
Operating System: Amazon Linux AMI 2018.03
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 7.503GiB
Name: ip-172-30-1-205
ID: YY74:M3ZE:4J6G:W5TW:HI2U:GIWX:3ZJ7:LAM5:K5T3:MHVN:7T3Z:LGQP
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

Answer 1

Turns out I was close with some of the previous attempts:
I made the mistake of not adding the #cloud-boothook line above #! /bin/bash.
And then I just added the sed -i '/^OPTIONS/s/"$/ --storage-opt dm.basesize=25G"/' /etc/sysconfig/docker line after cloud-init-per once docker_options
So eventually it looked like:
#cloud-boothook
#! /bin/bash
cloud-init-per once docker_options sed -i '/^OPTIONS/s/"$/ --storage-opt dm.basesize=25G"/' /etc/sysconfig/docker
And that worked.