--- description: Compose file reference keywords: fig, composition, compose version 1, docker title: Compose file version 1 reference toc_max: 4 toc_min: 1 sitemap: false --- ## Reference and guidelines These topics describe version 1 of the Compose file format. This is the oldest version. ## Compose and Docker compatibility matrix There are several versions of the Compose file format – 1, 2, 2.x, and 3.x The table below is a quick look. For full details on what each version includes and how to upgrade, see **[About versions and upgrading](compose-versioning.md)**. {% include content/compose-matrix.md %} ## Service configuration reference The Version 1 Compose file is a [YAML](https://yaml.org) file that defines [services](#service-configuration-reference). The default path for a Compose file is `./docker-compose.yml`. > **Tip**: You can use either a `.yml` or `.yaml` extension for this file. > They both work. A service definition contains configuration which is applied to each container started for that service, much like passing command-line parameters to `docker run`. As with `docker run`, options specified in the Dockerfile, such as `CMD`, `EXPOSE`, `VOLUME`, `ENV`, are respected by default - you don't need to specify them again in `docker-compose.yml`. This section contains a list of all configuration options supported by a service definition in version 1. ### build Configuration options that are applied at build time. `build` can specified as a string containing a path to the build context. ```yaml build: ./dir ``` > **Note** > > In [version 1 file format](compose-versioning.md#version-1), `build` is > different in two ways: > > * Only the string form (`build: .`) is allowed - not the object > form that is allowed in Version 2 and up. > * Using `build` together with [`image`](#image) is not allowed. > Attempting to do so results in an error. #### dockerfile Alternate Dockerfile. Compose uses an alternate file to build with. A build path must also be specified. ```yaml build: . dockerfile: Dockerfile-alternate ``` > **Note** > > In the [version 1 file format](compose-versioning.md#version-1), `dockerfile` > is different from newer versions in two ways: > > * It appears alongside `build`, not as a sub-option: > * Using `dockerfile` together with [`image`](#image) is not allowed. > Attempting to do so results in an error. ### cap_add, cap_drop Add or drop container capabilities. See `man 7 capabilities` for a full list. ```yaml cap_add: - ALL cap_drop: - NET_ADMIN - SYS_ADMIN ``` > **Note**: These options are ignored when > [deploying a stack in swarm mode](../../engine/reference/commandline/stack_deploy.md) > with a (version 3) Compose file. ### command Override the default command. ```yaml command: bundle exec thin -p 3000 ``` The command can also be a list, in a manner similar to [dockerfile](../../engine/reference/builder.md#cmd): ```yaml command: ["bundle", "exec", "thin", "-p", "3000"] ``` ### cgroup_parent Specify an optional parent cgroup for the container. ```yaml cgroup_parent: m-executor-abcd ``` ### container_name Specify a custom container name, rather than a generated default name. ```yaml container_name: my-web-container ``` Because Docker container names must be unique, you cannot scale a service beyond 1 container if you have specified a custom name. Attempting to do so results in an error. ### devices List of device mappings. Uses the same format as the `--device` docker client create option. ```yaml devices: - "/dev/ttyUSB0:/dev/ttyUSB0" ``` ### dns Custom DNS servers. Can be a single value or a list. ```yaml dns: 8.8.8.8 ``` ```yaml dns: - 8.8.8.8 - 9.9.9.9 ``` ### dns_search Custom DNS search domains. Can be a single value or a list. ```yaml dns_search: example.com ``` ```yaml dns_search: - dc1.example.com - dc2.example.com ``` ### entrypoint Override the default entrypoint. ```yaml entrypoint: /code/entrypoint.sh ``` The entrypoint can also be a list, in a manner similar to [dockerfile](../../engine/reference/builder.md#entrypoint): ```yaml entrypoint: ["php", "-d", "memory_limit=-1", "vendor/bin/phpunit"] ``` > **Note**: Setting `entrypoint` both overrides any default entrypoint set > on the service's image with the `ENTRYPOINT` Dockerfile instruction, *and* > clears out any default command on the image - meaning that if there's a `CMD` > instruction in the Dockerfile, it is ignored. ### env_file Add environment variables from a file. Can be a single value or a list. If you have specified a Compose file with `docker-compose -f FILE`, paths in `env_file` are relative to the directory that file is in. Environment variables declared in the [environment](#environment) section _override_ these values – this holds true even if those values are empty or undefined. ```yaml env_file: .env ``` ```yaml env_file: - ./common.env - ./apps/web.env - /opt/runtime_opts.env ``` Compose expects each line in an env file to be in `VAR=VAL` format. Lines beginning with `#` are processed as comments and are ignored. Blank lines are also ignored. ```console # Set Rails/Rack environment RACK_ENV=development ``` > **Note**: If your service specifies a [build](#build) option, variables > defined in environment files are _not_ automatically visible during the > build. The value of `VAL` is used as is and not modified at all. For example if the value is surrounded by quotes (as is often the case of shell variables), the quotes are included in the value passed to Compose. Keep in mind that _the order of files in the list is significant in determining the value assigned to a variable that shows up more than once_. The files in the list are processed from the top down. For the same variable specified in file `a.env` and assigned a different value in file `b.env`, if `b.env` is listed below (after), then the value from `b.env` stands. For example, given the following declaration in `docker-compose.yml`: ```yaml services: some-service: env_file: - a.env - b.env ``` And the following files: ```console # a.env VAR=1 ``` and ```console # b.env VAR=hello ``` `$VAR` is `hello`. ### environment Add environment variables. You can use either an array or a dictionary. Any boolean values (true, false, yes, no) need to be enclosed in quotes to ensure they are not converted to True or False by the YML parser. Environment variables with only a key are resolved to their values on the machine Compose is running on, which can be helpful for secret or host-specific values. ```yaml environment: RACK_ENV: development SHOW: 'true' SESSION_SECRET: ``` ```yaml environment: - RACK_ENV=development - SHOW=true - SESSION_SECRET ``` > **Note**: If your service specifies a [build](#build) option, variables > defined in `environment` are _not_ automatically visible during the > build. ### expose Expose ports without publishing them to the host machine - they'll only be accessible to linked services. Only the internal port can be specified. ```yaml expose: - "3000" - "8000" ``` ### extends Extend another service, in the current file or another, optionally overriding configuration. You can use `extends` on any service together with other configuration keys. The `extends` value must be a dictionary defined with a required `service` and an optional `file` key. ```yaml extends: file: common.yml service: webapp ``` The `service` the name of the service being extended, for example `web` or `database`. The `file` is the location of a Compose configuration file defining that service. If you omit the `file` Compose looks for the service configuration in the current file. The `file` value can be an absolute or relative path. If you specify a relative path, Compose treats it as relative to the location of the current file. You can extend a service that itself extends another. You can extend indefinitely. Compose does not support circular references and `docker-compose` returns an error if it encounters one. For more on `extends`, see the [the extends documentation](../extends.md#extending-services). ### external_links Link to containers started outside this `docker-compose.yml` or even outside of Compose, especially for containers that provide shared or common services. `external_links` follow semantics similar to `links` when specifying both the container name and the link alias (`CONTAINER:ALIAS`). ```yaml external_links: - redis_1 - project_db_1:mysql - project_db_1:postgresql ``` ### extra_hosts Add hostname mappings. Use the same values as the docker client `--add-host` parameter. ```yaml extra_hosts: - "somehost:162.242.195.82" - "otherhost:50.31.209.229" ``` An entry with the ip address and hostname is created in `/etc/hosts` inside containers for this service, e.g: ```console 162.242.195.82 somehost 50.31.209.229 otherhost ``` ### image Specify the image to start the container from. Can either be a repository/tag or a partial image ID. ```yaml image: redis ``` ```yaml image: ubuntu:18.04 ``` ```yaml image: tutum/influxdb ``` ```yaml image: example-registry.com:4000/postgresql ``` ```yaml image: a4bc65fd ``` If the image does not exist, Compose attempts to pull it, unless you have also specified [build](#build), in which case it builds it using the specified options and tags it with the specified tag. > **Note**: In the [version 1 file format](compose-versioning.md#version-1), > using [`build`](#build) together with `image` is not allowed. Attempting to do > so results in an error. ### labels Add metadata to containers using [Docker labels](../../config/labels-custom-metadata.md). You can use either an array or a dictionary. It's recommended that you use reverse-DNS notation to prevent your labels from conflicting with those used by other software. ```yaml labels: com.example.description: "Accounting webapp" com.example.department: "Finance" com.example.label-with-empty-value: "" ``` ```yaml labels: - "com.example.description=Accounting webapp" - "com.example.department=Finance" - "com.example.label-with-empty-value" ``` ### links Link to containers in another service. Either specify both the service name and a link alias (`"SERVICE:ALIAS"`), or just the service name. > Links are a legacy option. We recommend using > [networks](../networking.md) instead. ```yaml web: links: - "db" - "db:database" - "redis" ``` Containers for the linked service are reachable at a hostname identical to the alias, or the service name if no alias was specified. Links also express dependency between services in the same way as [depends_on](compose-file-v2.md#depends_on), so they determine the order of service startup. > **Note** > > If you define both links and [networks](index.md#networks), services with > links between them must share at least one network in common in order to > communicate. #### link environment variables > [Version 1 file format](compose-versioning.md#version-1) only. In version 2 and > up, custom networks are used, and no environment variables are created. > **Note** > > Environment variables are no longer the recommended method for connecting to > linked services. Instead, you should use the link name (by default, the name > of the linked service) as the hostname to connect to. Refer to the > [docker-compose.yml documentation](compose-file/index.md#links) for details. > > Environment variables are only populated if you use the > [legacy version 1 Compose file format](compose-file/compose-versioning.md#versioning). {: .warning } Compose uses [Docker links](../../network/links.md) to expose services' containers to one another. Each linked container injects a set of environment variables, each of which begins with the uppercase name of the container. To see what environment variables are available to a service, run `docker-compose run SERVICE env`. name\_PORT
Full URL, such as `DB_PORT=tcp://172.17.0.5:5432` name\_PORT\_num\_protocol
Full URL, such as `DB_PORT_5432_TCP=tcp://172.17.0.5:5432` name\_PORT\_num\_protocol\_ADDR
Container's IP address, such as `DB_PORT_5432_TCP_ADDR=172.17.0.5` name\_PORT\_num\_protocol\_PORT
Exposed port number, such as `DB_PORT_5432_TCP_PORT=5432` name\_PORT\_num\_protocol\_PROTO
Protocol (tcp or udp), such as `DB_PORT_5432_TCP_PROTO=tcp` name\_NAME
Fully qualified container name, such as `DB_1_NAME=/myapp_web_1/myapp_db_1` ### log_driver > [Version 1 file format](compose-versioning.md#version-1) only. In version 2 and up, use > [logging](index.md#logging). Specify a log driver. The default is `json-file`. ```yaml log_driver: syslog ``` ### log_opt > [Version 1 file format](compose-versioning.md#version-1) only. In version 2 and up, use > [logging](index.md#logging). Specify logging options as key-value pairs. An example of `syslog` options: ```yaml log_opt: syslog-address: "tcp://192.168.0.42:123" ``` ### net > [Version 1 file format](compose-versioning.md#version-1) only. In version 2 and up, use > [network_mode](index.md#network_mode) and [networks](index.md#networks). Network mode. Use the same values as the docker client `--net` parameter. The `container:...` form can take a service name instead of a container name or id. ```yaml net: "bridge" ``` ```yaml net: "host" ``` ```yaml net: "none" ``` ```yaml net: "service:[service name]" ``` ```yaml net: "container:[container name/id]" ``` ### pid ```yaml pid: "host" ``` 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 flag can access and manipulate other containers in the bare-metal machine's namespace and vice versa. ### ports Expose ports. Either specify both ports (`HOST:CONTAINER`), or just the container port (an ephemeral host port is chosen). > **Note**: When mapping ports in the `HOST:CONTAINER` format, you may experience > erroneous results when using a container port lower than 60, because YAML > parses numbers in the format `xx:yy` as a base-60 value. For this reason, > we recommend always explicitly specifying your port mappings as strings. ```yaml ports: - "3000" - "3000-3005" - "8000:8000" - "9090-9091:8080-8081" - "49100:22" - "127.0.0.1:8001:8001" - "127.0.0.1:5000-5010:5000-5010" - "6060:6060/udp" - "12400-12500:1240" ``` ### security_opt Override the default labeling scheme for each container. ```yaml security_opt: - label:user:USER - label:role:ROLE ``` ### stop_signal Sets an alternative signal to stop the container. By default `stop` uses SIGTERM. Setting an alternative signal using `stop_signal` causes `stop` to send that signal instead. ```yaml stop_signal: SIGUSR1 ``` ### ulimits Override the default ulimits for a container. You can either specify a single limit as an integer or soft/hard limits as a mapping. ```yaml ulimits: nproc: 65535 nofile: soft: 20000 hard: 40000 ``` ### volumes, volume\_driver Mount paths or named volumes, optionally specifying a path on the host machine (`HOST:CONTAINER`), or an access mode (`HOST:CONTAINER:ro`). For [version 2 files](compose-versioning.md#version-2), named volumes need to be specified with the [top-level `volumes` key](compose-file-v2.md#volume-configuration-reference). When using [version 1](compose-versioning.md#version-1), the Docker Engine creates the named volume automatically if it doesn't exist. You can mount a relative path on the host, which expands relative to the directory of the Compose configuration file being used. Relative paths should always begin with `.` or `..`. ```yaml volumes: # Just specify a path and let the Engine create a volume - /var/lib/mysql # Specify an absolute path mapping - /opt/data:/var/lib/mysql # Path on the host, relative to the Compose file - ./cache:/tmp/cache # User-relative path - ~/configs:/etc/configs/:ro # Named volume - datavolume:/var/lib/mysql ``` If you do not use a host path, you may specify a `volume_driver`. ```yaml volume_driver: mydriver ``` There are several things to note, depending on which [Compose file version](compose-versioning.md#versioning) you're using: - For [version 1 files](compose-versioning.md#version-1), both named volumes and container volumes use the specified driver. - No path expansion is done if you have also specified a `volume_driver`. For example, if you specify a mapping of `./foo:/data`, the `./foo` part is passed straight to the volume driver without being expanded. See [Docker Volumes](../../storage/volumes.md) and [Volume Plugins](/engine/extend/plugins_volume/) for more information. ### volumes_from Mount all of the volumes from another service or container, optionally specifying read-only access (``ro``) or read-write (``rw``). If no access level is specified, then read-write is used. ```yaml volumes_from: - service_name - service_name:ro ``` ### cpu\_shares, cpu\_quota, cpuset, domainname, hostname, ipc, mac\_address, mem\_limit, memswap\_limit, mem\_swappiness, privileged, read\_only, restart, shm\_size, stdin\_open, tty, user, working\_dir Each of these is a single value, analogous to its [docker run](../../engine/reference/run.md) counterpart. ```yaml cpu_shares: 73 cpu_quota: 50000 cpuset: 0,1 user: postgresql working_dir: /code domainname: foo.com hostname: foo ipc: host mac_address: 02:42:ac:11:65:43 mem_limit: 1000000000 memswap_limit: 2000000000 privileged: true restart: always read_only: true shm_size: 64M stdin_open: true tty: true ``` ## Compose documentation - [User guide](../index.md) - [Installing Compose](../install.md) - [Compose file versions and upgrading](compose-versioning.md) - [Sample apps with Compose](../samples-for-compose.md) - [Command line reference](../reference/index.md)