Cannot access private repositories using EC2 Container Service

Authentication is failing while attempting to use Amazon ECS (EC2 Container Service)

Authentication configuration in ecs.config is missing

In order for ECS to pull down docker images, the following needs to be in the ECS configuration file located at /etc/ecs/ecs.conf:

ECS_ENGINE_AUTH_TYPE=dockercfg
ECS_ENGINE_AUTH_DATA={"https://quay.io": {"auth": "YOURAUTHTOKENFROMDOCKERCFG", "email": "user@example.com"}}

If you are using a robot account, include the username as well:

ECS_ENGINE_AUTH_TYPE=dockercfg
ECS_ENGINE_AUTH_DATA={"https://quay.io": {"auth": "YOURAUTHTOKENFROMDOCKERCFG", "email": ".", "username": "USERNAME"}}

ECS_ENGINE_AUTH_DATA is the contents of the auths atttribute in .docker/config.json starting at Docker version 1.7.0 or the contents of .dockercfg before that.

Restart the ECS service to make the changes active.

See AWS documentation for more information.