Lono’s behavior can be tailored using a settings.yml file. This file should be created at ~/.lono/settings.yml or config/settings.yml within the project. The options from the files get merged with the following precedence:

  1. current folder - The current folder’s config/settings.yml values take the highest precedence.
  2. user - The user’s ~/.lono/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 lono/settings.yml:

# The base config is specially treated. It gets included the other environments automatically.
  # extract_scripts:
  #   to: "/opt"
  #   as: "ec2-user"
  # If s3_folder is set then the generated templates and app/scripts will automatically be uploaded to s3.
  # There are 2 formats for s3_folder:
  # Format 1:
  # s3_folder: mybucket/path/to/folder # simple string
  # Format 2:
  # s3_folder: # Hash options in order to support multiple AWS_PROFILEs
  #   default: mybucket/path
  #   aws_profile1: mybucket/path
  #   aws_profile2: another-bucket/storage/path
  # randomize_stack_name: true # tack on a 3 char random string at the end of the stack name for lono cfn create
  # s3_endpoint:  # Allows using a bucket in a different region than the stack.  Gets rid of WARNING: S3 client configured for "us-east-1" but the bucket "xxx" is in "us-west-2"; Please configure the proper region to avoid multiple unnecessary redirects and signing attempts.

  # 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

  # aws_profiles:
  #   - prod_profile

The table below covers what each setting does:

Setting Description
aws_profiles This provides a way to automatically map your AWS_PROFILE to a LONO_ENV. This prevents you from forgetting to switch your LONO_ENV when switching your AWS_PROFILE thereby accidentally launching a stack meant to be in the development account on the production account and vice versa. More details are explained in the LONO_ENV docs.
randomize_stack_name This is a convenience flag that results in lono automatically appending a random string to your stack name with the lono cfn lifecycle commands that speeds up your development flow when you are launching many stacks repeatedly. The random string gets appended to the stack name, but gets removed internally so that lono can use its conventions. It is explained in more detail below. Default: false
s3_folder This allows you to specify the base folder telling lono where to upload files to s3. app/scripts files are uploaded in the scripts subfolder in here and templates when using lono with nested stacks are uploaded in the templates subfolder.
extract_scripts This configures how the extract_scripts helper works. The extract_script helpers can take some options like to to specify where you want to extract app/scripts to. The default is /opt, so scripts end up in /opt/scripts.

The randomize_stack_name setting

The randomize_stack_name is an option that was added after realizing a common development flow pattern that was being repeatedly used. When working with CloudFormation templates and developing the source code, we must often launch stacks over and over as we fine tune the stack. Since we cannot launch a stack with a duplicate name it is useful to use a command like this:

lono cfn create my-stack-$(date +%s) --template my-stack

This command automatically adds a random string to the end of the stack name but uses the template name without the random string. The randomize_stack_name option automates this. So we can create multiple stacks with different names but the same source template rapidly. We can create multiple stacks in rapid-fire fashion and debug. When the option is enabled:

lono cfn create my-stack

Will create a “my-stack-[RANDOM]” using the my-stack template name. The random string is a short 3 character string.

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