Rancher 1.6 Docs

Environment Interpolation

Using Rancher Compose, environment variables from the machine running Rancher Compose can be used within the docker-compose.yml file. This is only supported in Rancher Compose commands and not in the Rancher UI.

How to use it in Docker-Compose.yml

Within the docker-compose.yml file, you can reference the environment variables on your machine. If there is no environment variable on the machine, it will replace the variable with a blank string. Rancher Compose will provide a warning on which environment variables are not set. If using environment variables for image tags, please note that Rancher Compose will not strip the : from the image to fetch the latest image. Since the image name, i.e. <imagename>: is an invalid image name, no container will be deployed. It’s up to the user to ensure that all environment variables are present and valid on the machine.

Example:

On our machine running Rancher Compose, we have an environment variable, IMAGE_TAG=14.04`.

# Image tag is set as environment variable
$ env | grep IMAGE
IMAGE_TAG=14.04
# Run Rancher Compose
$ rancher-compose up

Example docker-compose.yml

ubuntu:
  tty: true
  image: ubuntu:$IMAGE_TAG
  stdin_open: true

In Rancher, an Ubuntu service will be deployed with an ubuntu:14.04 image.

Environment Interpolation Formats

Rancher Compose supports the same formats as Docker Compose.

web:
  # unbracketed name
  image: "$IMAGE"

  # bracketed name
  command: "${COMMAND}"

  # array element
  ports:
  - "${HOST_PORT}:8000"

  # dictionary item value
  labels:
    mylabel: "${LABEL_VALUE}"

  # unset value - this will expand to "host-"
  hostname: "host-${UNSET_VALUE}"

  # escaped interpolation - this will expand to "${ESCAPED}"
  command: "$${ESCAPED}"