docker-compose/docs/Compose file reference (legacy)/compose-versioning.md

There are three legacy versions of the Compose file format:

• Version 1. This is specified by omitting a version key at the root of the YAML.

• Version 2.x. This is specified with a version: '2' or version: '2.1', etc., entry at the root of the YAML.

• Version 3.x, designed to be cross-compatible between Compose and the Docker Engine's swarm mode. This is specified with a version: '3' or version: '3.1', etc., entry at the root of the YAML.

The latest and recommended version of the Compose file format is defined by the Compose Specification. This format merges the 2.x and 3.x versions and is implemented by Compose 1.27.0+.

Note

If you're using multiple Compose files or extending services, each file must be of the same version - you cannot, for example, mix version 1 and 2 in a single project.

Several things differ depending on which version you use:

• The structure and permitted configuration keys
• The minimum Docker Engine version you must be running
• Compose's behaviour with regards to networking

These differences are explained below.

Version 2

Compose files using the version 2 syntax must indicate the version number at the root of the document. All services must be declared under the services key.

Version 2 files are supported by Compose 1.6.0+ and require a Docker Engine of version 1.10.0+.

Named volumes can be declared under the volumes key, and networks can be declared under the networks key.

By default, every container joins an application-wide default network, and is discoverable at a hostname that's the same as the service name. This means links are largely unnecessary. For more details, see Networking in Compose.

Note

With Compose version 2, when specifying the Compose file version to use, make sure to specify both the major and minor numbers. If no minor version is given, 0 is used by default and not the latest minor version. As a result, features added in later versions will not be supported. For example:

version: "2"

is equivalent to:

version: "2.0"

Simple example:

version: "{{% param "compose_file_v2" %}}"
services:
  web:
    build: .
    ports:
     - "8000:5000"
    volumes:
     - .:/code
  redis:
    image: redis

A more extended example, defining volumes and networks:

version: "{{% param "compose_file_v2" %}}"
services:
  web:
    build: .
    ports:
     - "8000:5000"
    volumes:
     - .:/code
    networks:
      - front-tier
      - back-tier
  redis:
    image: redis
    volumes:
      - redis-data:/var/lib/redis
    networks:
      - back-tier
volumes:
  redis-data:
    driver: local
networks:
  front-tier:
    driver: bridge
  back-tier:
    driver: bridge

Several other options were added to support networking, such as:

• aliases

• The depends_on option can be used in place of links to indicate dependencies between services and startup order.

  version: "{{% param "compose_file_v2" %}}" services:

  web:
    build: .
    depends_on:
      - db
      - redis
  redis:
    image: redis
  db:
    image: postgres
  

• ipv4_address, ipv6_address

Variable substitution also was added in Version 2.

Version 2.1

An upgrade of version 2 that introduces new parameters only available with Docker Engine version 1.12.0+. Version 2.1 files are supported by Compose 1.9.0+.

Introduces the following additional parameters:

• link_local_ips
• isolation in build configurations and service definitions
• labels for volumes, networks, and build
• name for volumes
• userns_mode
• healthcheck
• sysctls
• pids_limit
• oom_kill_disable
• cpu_period

Version 2.2

An upgrade of version 2.1 that introduces new parameters only available with Docker Engine version 1.13.0+. Version 2.2 files are supported by Compose 1.13.0+. This version also allows you to specify default scale numbers inside the service's configuration.

Introduces the following additional parameters:

• init
• scale
• cpu_rt_runtime and cpu_rt_period
• network for build configurations

Version 2.3

An upgrade of version 2.2 that introduces new parameters only available with Docker Engine version 17.06.0+. Version 2.3 files are supported by Compose 1.16.0+.

Introduces the following additional parameters:

• target, extra_hosts and shm_size for build configurations
• start_period for healthchecks
• "Long syntax" for volumes
• runtime for service definitions
• device_cgroup_rules

Version 2.4

An upgrade of version 2.3 that introduces new parameters only available with Docker Engine version 17.12.0+. Version 2.4 files are supported by Compose 1.21.0+.

Introduces the following additional parameters:

• platform for service definitions
• Support for extension fields at the root of service, network, and volume definitions

Version 3

Designed to be cross-compatible between Compose and the Docker Engine's swarm mode, version 3 removes several options and adds several more.

• Removed: volume_driver, volumes_from, cpu_shares, cpu_quota, cpuset, mem_limit, memswap_limit, extends, group_add. See the upgrading guide for how to migrate away from these.

• Added: deploy

If only the major version is given (version: '3'), the latest minor version is used by default.

Version 3.1

An upgrade of version 3 that introduces new parameters only available with Docker Engine version 1.13.1+, and higher.

Introduces the following additional parameters:

• secrets

Version 3.2

An upgrade of version 3 that introduces new parameters only available with Docker Engine version 17.04.0+, and higher.

Introduces the following additional parameters:

• cache_from in build configurations
• Long syntax for ports and volume mounts
• attachable network driver option
• deploy endpoint_mode
• deploy placement preference

Version 3.3

An upgrade of version 3 that introduces new parameters only available with Docker Engine version 17.06.0+, and higher.

Introduces the following additional parameters:

• build labels
• credential_spec
• configs

Version 3.4

An upgrade of version 3 that introduces new parameters. It is only available with Docker Engine version 17.09.0 and higher.

Introduces the following additional parameters:

• target and network in build configurations
• start_period for healthchecks
• order for update configurations
• name for volumes

Version 3.5

An upgrade of version 3 that introduces new parameters. It is only available with Docker Engine version 17.12.0 and higher.

Introduces the following additional parameters:

• isolation in service definitions
• name for networks, secrets and configs
• shm_size in build configurations

Version 3.6

An upgrade of version 3 that introduces new parameters. It is only available with Docker Engine version 18.02.0 and higher.

Introduces the following additional parameters:

• tmpfs size for tmpfs-type mounts

Version 3.7

An upgrade of version 3 that introduces new parameters. It is only available with Docker Engine version 18.06.0 and higher.

Introduces the following additional parameters:

• init in service definitions
• rollback_config in deploy configurations
• Support for extension fields at the root of service, network, volume, secret and config definitions

Version 3.8

An upgrade of version 3 that introduces new parameters. It is only available with Docker Engine version 19.03.0 and higher.

Introduces the following additional parameters:

• max_replicas_per_node in placement configurations
• template_driver option for config and secret configurations. This option is only supported when deploying swarm services using docker stack deploy.
• driver and driver_opts option for secret configurations. This option is only supported when deploying swarm services using docker stack deploy.

Version 1 (Deprecated)

Compose versions below 1.6.x are

Compose files that do not declare a version are considered "version 1". In those files, all the services are declared at the root of the document.

Version 1 is supported by Compose up to 1.6.x** and has been deprecated.

Version 1 files cannot declare named volumes, networks or build arguments.

Compose does not take advantage of networking when you use version 1: every container is placed on the default bridge network and is reachable from every other container at its IP address. You need to use links to enable discovery between containers.

Example:

web:
  build: .
  ports:
   - "8000:5000"
  volumes:
   - .:/code
  links:
   - redis
redis:
  image: redis

Upgrading

Version 2.x to 3.x

Between versions 2.x and 3.x, the structure of the Compose file is the same, but several options have been removed:

• volume_driver: Instead of setting the volume driver on the service, define a volume using the top-level volumes option and specify the driver there.

  version: "3.8"
  services:
    db:
      image: postgres
      volumes:
        - data:/var/lib/postgresql/data
  volumes:
    data:
      driver: mydriver
  

• volumes_from: To share a volume between services, define it using the top-level volumes option and reference it from each service that shares it using the service-level volumes option.

• cpu_shares, cpu_quota, cpuset, mem_limit, memswap_limit: These have been replaced by the resources key under deploy. deploy configuration only takes effect when using docker stack deploy, and is ignored by docker-compose.

• extends: This option has been removed for version: "3.x" Compose files. For more information on extends, see Extending services.

• group_add: This option has been removed for version: "3.x" Compose files.

• pids_limit: This option has not been introduced in version: "3.x" Compose files.

• link_local_ips in networks: This option has not been introduced in version: "3.x" Compose files.

Compatibility mode

docker-compose 1.20.0 introduces a new --compatibility flag designed to help developers transition to version 3 more easily. When enabled, docker-compose reads the deploy section of each service's definition and attempts to translate it into the equivalent version 2 parameter. Currently, the following deploy keys are translated:

• resources limits and memory reservations
• replicas
• restart_policy condition and max_attempts

All other keys are ignored and produce a warning if present. You can review the configuration that will be used to deploy by using the --compatibility flag with the config command.

Do not use this in production

We recommend against using --compatibility mode in production. The resulting configuration is only an approximate using non-Swarm mode properties, it may produce unexpected results.

Version 1 to 2.x

In the majority of cases, moving from version 1 to 2 is a very simple process:

1. Indent the whole file by one level and put a services: key at the top.
2. Add a version: '2' line at the top of the file.

It's more complicated if you're using particular configuration features:

• dockerfile: This now lives under the build key:

  build:
    context: .
    dockerfile: Dockerfile-alternate
  

• log_driver, log_opt: These now live under the logging key:

  logging:
    driver: syslog
    options:
      syslog-address: "tcp://192.168.0.42:123"
  

• links with environment variables: environment variables created by links, such as CONTAINERNAME_PORT, ` have been deprecated for some time. In the new Docker network system, they have been removed. You should either connect directly to the appropriate hostname or set the relevant environment variable yourself, using the link hostname:

  web:
    links:
      - db
    environment:
      - DB_PORT=tcp://db:5432
  

• external_links: Compose uses Docker networks when running version 2 projects, so links behave slightly differently. In particular, two containers must be connected to at least one network in common in order to communicate, even if explicitly linked together.

  Either connect the external container to your app's default network, or connect both the external container and your service's containers to an external network.

• net: This is now replaced by network_mode:

  net: host    ->  network_mode: host
  net: bridge  ->  network_mode: bridge
  net: none    ->  network_mode: none
  

  If you're using net: "container:[service name]", you must now use network_mode: "service:[service name]" instead.

  net: "container:web"  ->  network_mode: "service:web"
  

  If you're using net: "container:[container name/id]", the value does not need to change.

  net: "container:cont-name"  ->  network_mode: "container:cont-name"
  net: "container:abc12345"   ->  network_mode: "container:abc12345"
  

• volumes with named volumes: these must now be explicitly declared in a top-level volumes section of your Compose file. If a service mounts a named volume called data, you must declare a data volume in your top-level volumes section. The whole file might look like this:

  version: "{{% param "compose_file_v2" %}}"
  services:
    db:
      image: postgres
      volumes:
        - data:/var/lib/postgresql/data
  volumes:
    data: {}
  

  By default, Compose creates a volume whose name is prefixed with your project name. If you want it to just be called data, declare it as external:

  volumes:
    data:
      external: true