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Docker Compose is a tool for running multi-container applications on Docker defined using the Compose file format.A Compose file is used to define how the one or more containers that make up your application are configured. Under Docker 19.03.0 Beta 2, support for NVIDIA GPU has been introduced in the form of new CLI API -gpus. Docker/cli#1714 talk about this enablement. Now one can simply pass -gpus option for GPU-accelerated Docker based application. 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+. V2 and v3 Declaration. Note: When specifying the Compose file version to use, make sure to specify both the major and minor numbers.

The Compose file is a YAML file defining services,networks, and volumes for a Docker application.

The Compose file formats are now described in these references, specific to each version.

The topics below explain the differences among the versions, Docker Enginecompatibility, and how to upgrade.

Compatibility matrix

There are several versions of the Compose file format – 1, 2, 2.x, and 3.x

This table shows which Compose file versions support specific Docker releases.

In addition to Compose file format versions shown in the table, the Composeitself is on a release schedule, as shown in Composereleases, but file format versionsdo not necessarily increment with each release. For example, Compose file format3.0 was first introduced in Compose release1.10.0, and versionedgradually in subsequent releases.

The latest Compose file format is defined by the Compose Specification and is implemented by Docker Compose 1.27.0+.

Looking for more detail on Docker and Compose compatibility?

We recommend keeping up-to-date with newer releases as much as possible.However, if you are using an older version of Docker and want to determine whichCompose release is compatible, refer to the Compose releasenotes. Each set of release notesgives details on which versions of Docker Engine are supported, alongwith compatible Compose file format versions. (See also, the discussion inissue #3404.)

For details on versions and how to upgrade, seeVersioning andUpgrading.

Versioning

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’sswarm 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+.

Latest Version Of Docker Compose

v2 and v3 Declaration

Note: When specifying the Compose file version to use, make sure tospecify both the major and minor numbers. If no minor version is given,0 is used by default and not the latest minor version.

The Compatibility Matrix shows Compose file versions mapped to Docker Engine releases.

To move your project to a later version, see the Upgradingsection.

Note: If you’re usingmultiple Compose files orextending services, each file must be of thesame version - you cannot, for example, mix version 1 and 2 in a singleproject.

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 1 (Deprecated)

Compose files that do not declare a version are considered “version 1”. In thosefiles, all the services aredeclared at the root of the document.

Version 1 is supported by Compose up to 1.6.x. It will be deprecated in afuture Compose release.

Version 1 files cannot declare namedvolumes, networks orbuild arguments.

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

Example:

Version 2

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

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

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

By default, every container joins an application-wide default network, and isdiscoverable at a hostname that’s the same as the service name. This meanslinks are largely unnecessary. For more details, seeNetworking in Compose.

Note

When specifying the Compose file version to use, make sure tospecify 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:

is equivalent to:

Simple example:

A more extended example, defining volumes and networks:

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

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

Variable substitution also was added in Version 2.

Version 2.1

An upgrade of version 2 that introduces new parameters onlyavailable with Docker Engine version 1.12.0+. Version 2.1 files aresupported by Compose 1.9.0+.

Introduces the following additional parameters:

• isolation in build configurations andservice definitions
• labels for volumes,networks, andbuild
• name for volumes

Version 2.2

An upgrade of version 2.1 that introduces new parameters onlyavailable with Docker Engine version 1.13.0+. Version 2.2 files aresupported by Compose 1.13.0+. This version also allows you to specifydefault scale numbers inside the service’s configuration.

Introduces the following additional parameters:

• network for build configurations

Version 2.3

An upgrade of version 2.2 that introduces new parameters onlyavailable with Docker Engine version 17.06.0+. Version 2.3 files aresupported by Compose 1.16.0+.

Introduces the following additional parameters:

• target, extra_hosts andshm_size for build configurations
• start_period for healthchecks
• runtime for service definitions

Version 2.4

An upgrade of version 2.3 that introduces new parameters onlyavailable with Docker Engine version 17.12.0+. Version 2.4 files aresupported 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 volumedefinitions

Version 3

Designed to be cross-compatible between Compose and the Docker Engine’sswarm mode, version 3 removes several options and addsseveral more.

• Removed: volume_driver, volumes_from, cpu_shares, cpu_quota,cpuset, mem_limit, memswap_limit, extends, group_add. Seethe upgrading guide for how to migrate away from these.(For more information on extends, see Extending services.)

• Added: deploy

Note: When specifying the Compose file version to use, make sure tospecify 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 inlater versions will not be supported. For example:

is equivalent to:

Version 3.1

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

Introduces the following additional parameters:

Version 3.2

An upgrade of version 3 that introduces new parameters onlyavailable 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

Version 3.3

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

Introduces the following additional parameters:

Version 3.4

Docker Compose Version Latest Version

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

Introduces the following additional parameters:

• target and network inbuild 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 isonly 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 isonly 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 isonly 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, secretand config definitions

Version 3.8

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

Introduces the following additional parameters:

• max_replicas_per_node in placementconfigurations
• 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.

Upgrading

Version 2.x to 3.x

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

• volume_driver: Instead of setting the volume driver on the service, definea volume using thetop-level volumes optionand specify the driver there.

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

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

• extends: This option has been removed for version: '3.x'Compose files. (For more information, 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 inversion: '3.x' Compose files.

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:

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

• links with environment variables: environment variables created bylinks, 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 theappropriate hostname or set the relevant environment variable yourself,using the link hostname:

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

  Either connect the external container to your app’sdefault network, or connect both the external container andyour service’s containers to anexternal network.

• net: This is now replaced by network_mode:

  If you’re using net: 'container:[service name]', you must now usenetwork_mode: 'service:[service name]' instead.

  If you’re using net: 'container:[container name/id]', the value does notneed to change.

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

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

Compatibility mode

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

• resources limits and memory reservations
• restart_policycondition and max_attempts

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

Do not use this in production!

We recommend against using --compatibility mode in production. Because theresulting configuration is only an approximate using non-Swarm modeproperties, it may produce unexpected results.

Compose file format references