Stack file YAML reference

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A stack is a collection of services that make up an application in a specific environment. Learn more about stacks here. A stack file is a file in YAML format that defines one or more services, similar to a docker-compose.yml file but with a few extensions. The default name for this file is docker-cloud.yml.

Stack file example

Below is an example docker-cloud.yml:

lb:
  image: dockercloud/haproxy
  links:
    - web
  ports:
    - "80:80"
  roles:
    - global
web:
  image: dockercloud/quickstart-python
  links:
    - redis
  target_num_containers: 4
redis:
  image: redis

Each key defined in docker-cloud.yml creates a service with that name in Docker Cloud. In the example above, three services are created: lb, web and redis. Each service is a dictionary whose possible keys are documented below.

The image key is mandatory. Other keys are optional and are analogous to their Docker Cloud Service API counterparts.

image (required)

The image used to deploy this service. This is the only mandatory key.

image: drupal
image: dockercloud/hello-world
image: my.registry.com/redis

autodestroy

Whether the containers for this service should be terminated if they stop (default: no, possible values: no, on-success, always).

autodestroy: always

autoredeploy

Whether to redeploy the containers of the service when its image is updated in Docker Cloud registry (default: false).

autoredeploy: true

cap_add, cap_drop

Add or drop container capabilities. See man 7 capabilities for a full list.

cap_add:
  - ALL
cap_drop:
  - NET_ADMIN
  - SYS_ADMIN

cgroup_parent

Specify an optional parent cgroup for the container.

cgroup_parent: m-executor-abcd

command

Override the default command in the image.

command: echo 'Hello World!'

deployment_strategy

Container distribution among nodes (default: emptiest_node, possible values: emptiest_node, high_availability, every_node). Learn more here.

deployment_strategy: high_availability

devices

List of device mappings. Uses the same format as the --device docker client create option.

devices:
  - "/dev/ttyUSB0:/dev/ttyUSB0"

dns

Specify custom DNS servers. Can be a single value or a list.

dns: 8.8.8.8
dns:
  - 8.8.8.8
  - 9.9.9.9

dns_search

Specify custom DNS search domains. Can be a single value or a list.

dns_search: example.com
dns_search:
  - dc1.example.com
  - dc2.example.com

environment

A list of environment variables to add in the service’s containers at launch. The environment variables specified here override any image-defined environment variables. You can use either an array or a dictionary format.

Dictionary format: yml environment: PASSWORD: my_password

Array format: yml environment: - PASSWORD=my_password

When you use the Docker Cloud CLI to create a stack, you can use the environment variables defined locally in your shell to define those in the stack. This is useful if you don’t want to store passwords or other sensitive information in your stack file:

environment:
  - PASSWORD

expose

Expose ports without publishing them to the host machine - they’ll only be accessible from your nodes in Docker Cloud. udp ports can be specified with a /udp suffix.

expose:
 - "80"
 - "90/udp"

extra_hosts

Add hostname mappings. Use the same values as the docker client --add-host parameter.

extra_hosts:
  - "somehost:162.242.195.82"
  - "otherhost:50.31.209.229"

labels

Add metadata to containers using Docker Engine labels. You can use either an array or a dictionary.

We recommend using reverse-DNS notation to prevent your labels from conflicting with those used by other software.

labels:
  com.example.description: "Accounting webapp"
  com.example.department: "Finance"
  com.example.label-with-empty-value: ""

labels:
  - "com.example.description=Accounting webapp"
  - "com.example.department=Finance"
  - "com.example.label-with-empty-value"

Link to another service.

Either specify both the service unique name and the link alias (SERVICE:ALIAS), or just the service unique name (which will also be used for the alias). If a service you want to link to is part of a different stack, specify the external stack name too.

  • If the target service belongs to this stack, its service unique name is its service name.
  • If the target service does not belong to any stacks (it is a standalone service), its service unique name is its service name.
  • If the target service belongs to another stack, its service unique name is its service name plus the service stack name, separated by a period (.).
links:
 - mysql
 - redis:cache
 - amqp.staging:amqp

Environment variables are created for each link that Docker Cloud resolves to the containers IPs of the linked service. More information here.

net

Networking mode. Only “bridge” and “host” options are supported for now.

net: host

pid

Sets the PID mode to the host PID mode. This turns on sharing between container and the host operating system the PID address space. Containers launched with this (optional) flag will be able to access and be accessed by other containers in the namespace belonging to the host running the Docker daemon.

pid: "host"

ports

Expose ports. Either specify both ports (HOST:CONTAINER), or just the container port (a random host port will be chosen). udp ports can be specified with a /udp suffix.

ports:
 - "80"
 - "443:443"
 - "500/udp"
 - "4500:4500/udp"
 - "49022:22"

privileged

Whether to start the containers with Docker Engine’s privileged flag set or not (default: false).

privileged: true

restart

Whether the containers for this service should be restarted if they stop (default: no, possible values: no, on-failure, always).

restart: always

roles

A list of Docker Cloud API roles to grant the service. The only supported value is global, which creates an environment variable DOCKERCLOUD_AUTH used to authenticate against Docker Cloud API. Learn more here.

roles:
 - global

security_opt

Override the default labeling scheme for each container.

security_opt:
  - label:user:USER
  - label:role:ROLE

sequential_deployment

Whether the containers should be launched and scaled in sequence (default: false). Learn more here.

sequential_deployment: true

tags

Indicates the deploy tags to select the nodes where containers are created.

tags:
 - staging
 - web

target_num_containers

The number of containers to run for this service (default: 1).

target_num_containers: 3

volumes

Mount paths as volumes, optionally specifying a path on the host machine (HOST:CONTAINER), or an access mode (HOST:CONTAINER:ro).

volumes:
 - /etc/mysql
 - /sys:/sys
 - /etc:/etc:ro

volumes_from

Mount all of the volumes from another service by specifying a service unique name. If the target service belongs to this stack its service unique name is its service name. If the target service does not belong to any stack its service unique name is its service name. If the target service belongs to another stack its service unique name is its service name plus the service stack name, separated by “.”. Learn more here.

volumes_from:
 - database
 - mongodb.staging

Single value keys analogous to a docker run counterpart

working_dir: /app
entrypoint: /app/entrypoint.sh
user: root
hostname: foo
domainname: foo.com
mac_address: 02:42:ac:11:65:43
cpu_shares: 512
cpuset: 0,1
mem_limit: 100000m
memswap_limit: 200000m
privileged: true
read_only: true
stdin_open: true
tty: true

Unsupported Docker-compose keys

Stack files (docker-cloud.yml) were designed with docker-compose.yml in mind to maximize compatibility. However the following keys used in Compose are not supported in Docker Cloud stackfiles:

build
external_links
env_file
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