mirror of
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7b109bc026
People are likely to run into their env vars being set to empty strings, if they're not aware that they need to escape them for Compose to not interpolate them. Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>
452 lines
12 KiB
Markdown
452 lines
12 KiB
Markdown
<!--[metadata]>
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+++
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title = "Compose file reference"
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description = "Compose file reference"
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keywords = ["fig, composition, compose, docker"]
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aliases = ["/compose/yml"]
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[menu.main]
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parent="smn_compose_ref"
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+++
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<![end-metadata]-->
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# Compose file reference
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The compose file is a [YAML](http://yaml.org/) file where all the top level
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keys are the name of a service, and the values are the service definition.
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The default path for a compose file is `./docker-compose.yml`.
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Each service defined in `docker-compose.yml` must specify exactly one of
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`image` or `build`. Other keys are optional, and are analogous to their
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`docker run` command-line counterparts.
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As with `docker run`, options specified in the Dockerfile (e.g., `CMD`,
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`EXPOSE`, `VOLUME`, `ENV`) are respected by default - you don't need to
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specify them again in `docker-compose.yml`.
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### build
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Path to a directory containing a Dockerfile. When the value supplied is a
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relative path, it is interpreted as relative to the location of the yml file
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itself. This directory is also the build context that is sent to the Docker daemon.
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Compose will build and tag it with a generated name, and use that image thereafter.
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build: /path/to/build/dir
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Using `build` together with `image` is not allowed. Attempting to do so results in an error.
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### cap_add, cap_drop
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Add or drop container capabilities.
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See `man 7 capabilities` for a full list.
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cap_add:
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- ALL
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cap_drop:
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- NET_ADMIN
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- SYS_ADMIN
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### command
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Override the default command.
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command: bundle exec thin -p 3000
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### cgroup_parent
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Specify an optional parent cgroup for the container.
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cgroup_parent: m-executor-abcd
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### container_name
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Specify a custom container name, rather than a generated default name.
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container_name: my-web-container
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Because Docker container names must be unique, you cannot scale a service
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beyond 1 container if you have specified a custom name. Attempting to do so
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results in an error.
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### devices
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List of device mappings. Uses the same format as the `--device` docker
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client create option.
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devices:
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- "/dev/ttyUSB0:/dev/ttyUSB0"
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### dns
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Custom DNS servers. Can be a single value or a list.
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dns: 8.8.8.8
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dns:
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- 8.8.8.8
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- 9.9.9.9
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### dns_search
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Custom DNS search domains. Can be a single value or a list.
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dns_search: example.com
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dns_search:
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- dc1.example.com
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- dc2.example.com
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### dockerfile
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Alternate Dockerfile.
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Compose will use an alternate file to build with.
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dockerfile: Dockerfile-alternate
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Using `dockerfile` together with `image` is not allowed. Attempting to do so results in an error.
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### env_file
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Add environment variables from a file. Can be a single value or a list.
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If you have specified a Compose file with `docker-compose -f FILE`, paths in
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`env_file` are relative to the directory that file is in.
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Environment variables specified in `environment` override these values.
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env_file: .env
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env_file:
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- ./common.env
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- ./apps/web.env
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- /opt/secrets.env
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Compose expects each line in an env file to be in `VAR=VAL` format. Lines
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beginning with `#` (i.e. comments) are ignored, as are blank lines.
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# Set Rails/Rack environment
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RACK_ENV=development
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### environment
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Add environment variables. You can use either an array or a dictionary. Any
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boolean values; true, false, yes no, need to be enclosed in quotes to ensure
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they are not converted to True or False by the YML parser.
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Environment variables with only a key are resolved to their values on the
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machine Compose is running on, which can be helpful for secret or host-specific values.
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environment:
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RACK_ENV: development
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SHOW: 'true'
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SESSION_SECRET:
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environment:
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- RACK_ENV=development
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- SHOW=true
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- SESSION_SECRET
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### expose
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Expose ports without publishing them to the host machine - they'll only be
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accessible to linked services. Only the internal port can be specified.
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expose:
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- "3000"
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- "8000"
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### extends
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Extend another service, in the current file or another, optionally overriding
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configuration.
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Here's a simple example. Suppose we have 2 files - **common.yml** and
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**development.yml**. We can use `extends` to define a service in
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**development.yml** which uses configuration defined in **common.yml**:
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**common.yml**
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webapp:
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build: ./webapp
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environment:
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- DEBUG=false
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- SEND_EMAILS=false
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**development.yml**
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web:
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extends:
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file: common.yml
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service: webapp
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ports:
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- "8000:8000"
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links:
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- db
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environment:
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- DEBUG=true
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db:
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image: postgres
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Here, the `web` service in **development.yml** inherits the configuration of
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the `webapp` service in **common.yml** - the `build` and `environment` keys -
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and adds `ports` and `links` configuration. It overrides one of the defined
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environment variables (DEBUG) with a new value, and the other one
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(SEND_EMAILS) is left untouched.
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The `file` key is optional, if it is not set then Compose will look for the
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service within the current file.
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For more on `extends`, see the [tutorial](extends.md#example) and
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[reference](extends.md#reference).
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### external_links
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Link to containers started outside this `docker-compose.yml` or even outside
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of Compose, especially for containers that provide shared or common services.
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`external_links` follow semantics similar to `links` when specifying both the
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container name and the link alias (`CONTAINER:ALIAS`).
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external_links:
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- redis_1
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- project_db_1:mysql
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- project_db_1:postgresql
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### extra_hosts
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Add hostname mappings. Use the same values as the docker client `--add-host` parameter.
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extra_hosts:
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- "somehost:162.242.195.82"
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- "otherhost:50.31.209.229"
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An entry with the ip address and hostname will be created in `/etc/hosts` inside containers for this service, e.g:
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162.242.195.82 somehost
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50.31.209.229 otherhost
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### image
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Tag or partial image ID. Can be local or remote - Compose will attempt to
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pull if it doesn't exist locally.
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image: ubuntu
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image: orchardup/postgresql
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image: a4bc65fd
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### labels
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Add metadata to containers using [Docker labels](http://docs.docker.com/userguide/labels-custom-metadata/). You can use either an array or a dictionary.
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It's recommended that you use reverse-DNS notation to prevent your labels from conflicting with those used by other software.
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labels:
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com.example.description: "Accounting webapp"
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com.example.department: "Finance"
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com.example.label-with-empty-value: ""
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labels:
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- "com.example.description=Accounting webapp"
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- "com.example.department=Finance"
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- "com.example.label-with-empty-value"
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### links
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Link to containers in another service. Either specify both the service name and
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the link alias (`SERVICE:ALIAS`), or just the service name (which will also be
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used for the alias).
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links:
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- db
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- db:database
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- redis
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An entry with the alias' name will be created in `/etc/hosts` inside containers
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for this service, e.g:
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172.17.2.186 db
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172.17.2.186 database
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172.17.2.187 redis
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Environment variables will also be created - see the [environment variable
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reference](env.md) for details.
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### log_driver
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Specify a logging driver for the service's containers, as with the ``--log-driver``
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option for docker run ([documented here](https://docs.docker.com/reference/logging/overview/)).
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The default value is json-file.
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log_driver: "json-file"
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log_driver: "syslog"
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log_driver: "none"
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> **Note:** Only the `json-file` driver makes the logs available directly from
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> `docker-compose up` and `docker-compose logs`. Using any other driver will not
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> print any logs.
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### log_opt
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Specify logging options with `log_opt` for the logging driver, as with the ``--log-opt`` option for `docker run`.
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Logging options are key value pairs. An example of `syslog` options:
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log_driver: "syslog"
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log_opt:
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syslog-address: "tcp://192.168.0.42:123"
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### net
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Networking mode. Use the same values as the docker client `--net` parameter.
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net: "bridge"
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net: "none"
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net: "container:[name or id]"
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net: "host"
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### pid
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pid: "host"
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Sets the PID mode to the host PID mode. This turns on sharing between
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container and the host operating system the PID address space. Containers
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launched with this flag will be able to access and manipulate other
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containers in the bare-metal machine's namespace and vise-versa.
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### ports
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Expose ports. Either specify both ports (`HOST:CONTAINER`), or just the container
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port (a random host port will be chosen).
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> **Note:** When mapping ports in the `HOST:CONTAINER` format, you may experience
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> erroneous results when using a container port lower than 60, because YAML will
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> parse numbers in the format `xx:yy` as sexagesimal (base 60). For this reason,
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> we recommend always explicitly specifying your port mappings as strings.
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ports:
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- "3000"
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- "3000-3005"
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- "8000:8000"
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- "9090-9091:8080-8081"
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- "49100:22"
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- "127.0.0.1:8001:8001"
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- "127.0.0.1:5000-5010:5000-5010"
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### security_opt
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Override the default labeling scheme for each container.
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security_opt:
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- label:user:USER
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- label:role:ROLE
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### volumes, volume\_driver
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Mount paths as volumes, optionally specifying a path on the host machine
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(`HOST:CONTAINER`), or an access mode (`HOST:CONTAINER:ro`).
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volumes:
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- /var/lib/mysql
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- ./cache:/tmp/cache
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- ~/configs:/etc/configs/:ro
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You can mount a relative path on the host, which will expand relative to
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the directory of the Compose configuration file being used. Relative paths
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should always begin with `.` or `..`.
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If you use a volume name (instead of a volume path), you may also specify
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a `volume_driver`.
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volume_driver: mydriver
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> Note: No path expansion will be done if you have also specified a
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> `volume_driver`.
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See [Docker Volumes](https://docs.docker.com/userguide/dockervolumes/) and
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[Volume Plugins](https://docs.docker.com/extend/plugins_volume/) for more
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information.
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### volumes_from
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Mount all of the volumes from another service or container, optionally
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specifying read-only access(``ro``) or read-write(``rw``).
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volumes_from:
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- service_name
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- container_name
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- service_name:rw
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### cpu\_shares, cpuset, domainname, entrypoint, hostname, ipc, mac\_address, mem\_limit, memswap\_limit, privileged, read\_only, restart, stdin\_open, tty, user, working\_dir
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Each of these is a single value, analogous to its
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[docker run](https://docs.docker.com/reference/run/) counterpart.
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cpu_shares: 73
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cpuset: 0,1
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entrypoint: /code/entrypoint.sh
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user: postgresql
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working_dir: /code
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domainname: foo.com
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hostname: foo
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ipc: host
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mac_address: 02:42:ac:11:65:43
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mem_limit: 1000000000
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memswap_limit: 2000000000
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privileged: true
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restart: always
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read_only: true
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stdin_open: true
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tty: true
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## Variable substitution
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Your configuration options can contain environment variables. Compose uses the
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variable values from the shell environment in which `docker-compose` is run. For
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example, suppose the shell contains `POSTGRES_VERSION=9.3` and you supply this
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configuration:
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db:
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image: "postgres:${POSTGRES_VERSION}"
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When you run `docker-compose up` with this configuration, Compose looks for the
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`POSTGRES_VERSION` environment variable in the shell and substitutes its value
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in. For this example, Compose resolves the `image` to `postgres:9.3` before
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running the configuration.
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If an environment variable is not set, Compose substitutes with an empty
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string. In the example above, if `POSTGRES_VERSION` is not set, the value for
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the `image` option is `postgres:`.
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Both `$VARIABLE` and `${VARIABLE}` syntax are supported. Extended shell-style
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features, such as `${VARIABLE-default}` and `${VARIABLE/foo/bar}`, are not
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supported.
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You can use a `$$` (double-dollar sign) when your configuration needs a literal
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dollar sign. This also prevents Compose from interpolating a value, so a `$$`
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allows you to refer to environment variables that you don't want processed by
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Compose.
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web:
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build: .
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command: "$$VAR_NOT_INTERPOLATED_BY_COMPOSE"
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If you forget and use a single dollar sign (`$`), Compose interprets the value as an environment variable and will warn you:
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The VAR_NOT_INTERPOLATED_BY_COMPOSE is not set. Substituting an empty string.
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## Compose documentation
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- [User guide](index.md)
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- [Installing Compose](install.md)
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- [Get started with Django](django.md)
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- [Get started with Rails](rails.md)
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- [Get started with WordPress](wordpress.md)
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- [Command line reference](./reference/index.md)
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