The behavior of ufo can be configured with a settings.yml file. A starter project .ufo/settings.yml file is generated as part of the ufo init command. There are can be multiple settings files. The options from the files get merged and respected in the following precedence:

  1. current folder - The current folder’s .ufo/settings.yml values take the highest precedence.
  2. user - The user’s ~/.ufo/settings.yml values take the second highest precedence.
  3. default - The default settings bundled with the tool takes the lowest precedence.

Let’s take a look at an example settings.yml:

  image: tongueroo/demo-ufo
  # clean_keep: 30 # cleans up docker images on your docker server.
  # ecr_keep: 30 # cleans up images on ECR and keeps this remaining amount. Defaults to keep all.
  network_profile: default # .ufo/settings/network/default.yml file
  cfn_profile: default # .ufo/settings/cfn/default.yml file

  # cluster: dev # uncomment if you want the cluster name be other than the default
                 # the default is to match UFO_ENV.  So UFO_ENV=development means the ECS
                 # cluster will be name development
  # When you have AWS_PROFILE set to one of these values, ufo will switch to the desired
  # environment. This prevents you from switching AWS_PROFILE, forgetting to
  # also switch UFO_ENV, and accidentally deploying to production vs development.
  # aws_profiles:
  #   - dev_profile1
  #   - dev_profile2

  # cluster: prod
  # aws_profiles:
  #   - prod_profile

The table below covers each setting:

Setting Description
aws_profiles If you have the AWS_PROFILE environment variable set, this will ensure that you are deploying the right UFO_ENV to the right AWS environment. It is explained below.
cfn_profile The name of the cfn profile settings file to use. Maps to .ufo/settings/cfn/NAME.yml file
clean_keep Docker images generated from ufo are cleaned up automatically for you at the end of ufo ship. This controls how many docker images to keep around. The default is 3.
cluster By convention, the ECS cluster that ufo deploys to matches the UFO_ENV. If UFO=development, then ufo ship deploys to the development ECS cluster. This is option overrides this convention.
ecr_keep If you are using AWS ECR, then the ECR images can also be automatically cleaned up at the end of ufo ship. By default this is set to nil and all AWS ECR are kept.
image The image value is the name that ufo will use for the Docker image name to be built. Only provide the basename part of the image name without the tag because ufo automatically generates the tag for you. For example, tongueroo/demo-ufo is correct and tongueroo/demo-ufo:my-tag is incorrect.
network_profile The name of the network profile settings file to use. Maps to .ufo/settings/network/NAME.yml file

ECS Cluster Convention

Normally, the ECS cluster defaults to whatever UFO_ENV is set to by convention. For example, when UFO_ENV=production the ECS Cluster is production and when UFO_ENV=development the ECS Cluster is development. There are several ways to override this behavior. Let’s go through an example:

By default, these are all the same:

ufo ship demo-web
UFO_ENV=development ufo ship demo-web # same
UFO_ENV=development ufo ship demo-web --cluster development # same

If you use a specific UFO_ENV=production, these are the same

UFO_ENV=production ufo ship demo-web
UFO_ENV=production ufo ship demo-web --cluster production # same

Override the convention by explicitly specifying the --cluster option in the CLI.

ufo ship demo-web --cluster custom-cluster # override the cluster
UFO_ENV=production ufo ship demo-web --cluster production-cluster # override the cluster

Override the convention by setting the cluster option in the settings.yml file, so you won’t have to specify the --cluster option in the command repeatedly.

  cluster: dev

  cluster: prod


An interesting option is aws_profiles. Here’s an example:

    - dev-profile1
    - dev-profile2

    - prod-profile

In this case, when you set the environment variable AWS_PROFILE to switch AWS profiles in your shell, ufo picks this up and maps the AWS_PROFILE value to the specified UFO_ENV using the aws_profiles option. Example:

AWS_PROFILE=dev-profile1 => UFO_ENV=development
AWS_PROFILE=dev-profile2 => UFO_ENV=development
AWS_PROFILE=prod-profile => UFO_ENV=production

This behavior prevents you from switching AWS_PROFILEs, forgetting to switch UFO_ENV and then accidentally deploying a production based docker image to development and vice versa because you forgot to also switch UFO_ENV to its respective environment.

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