Docker-compose Compose Guide (V3.7)

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A basic introduction to docker for docker-compose installation is beyond the scope of this article.

This article is basically a strict English-Chinese translation of the Docker-compose YAML file format. I did this yesterday because I thought of scanning the docker-compose layout for how to use ${PWD}. The Chinese version was not helpful, but the official website finally solved my ambiguity. Therefore, I think a rigorous translation and explanation should be made to explain the details of docker-compose arrangement.

Below, we will focus on the details of version 3 of the Docker-compose orchestration file format.

Reading this article, you should have a basic understanding of Docker-compose, or at least a basic understanding of the early (version 2) choreography format.

About the authorization

Translation from belong to the original docs.docker.com/compose/com… .

The https://github.com/hedzr/docker-compose-file-format itself to distribute MIT way.

Choreography version 3

history

Version 3 is the format docker-Compose has supported since docker-Engine 1.13. Before this, Docker launched swarm Mode in 1.12 to build virtual computing resources in a virtual network, and greatly improved docker’s network and storage support.

The following table (from the official website) provides a clear contrast between docker-compose and Docker-engine.

Compose file format	Docker Engine release
3.7	18.06.0 +
3.6	18.02.0 +
3.5	17.12.0 +
3.4	17.09.0 +
3.3	17.06.0 +
3.2	17.04.0 +
3.1	1.13.1 +
3.0	1.13.0 +
2.4	17.12.0 +
2.3	17.06.0 +
2.2	1.13.0 +
2.1	1.12.0 +
2.0	1.10.0 +
1.0	1.9.1. +

Choreograph file structures with examples

Here is a sample of a typical file structure for version 3+ :

version: "3.7"
services:

  redis:
    image: redis:alpine
    ports:
      - "6379"
    networks:
      - frontend
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  db:
    image: Postgres: 9.4
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - backend
    deploy:
      placement:
        constraints: [node.role = = manager]

  vote:
    image: dockersamples/examplevotingapp_vote:before
    ports:
      - "5000:80"
    networks:
      - frontend
    depends_on:
      - redis
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
      restart_policy:
        condition: on-failure

  result:
    image: dockersamples/examplevotingapp_result:before
    ports:
      - "5001:80"
    networks:
      - backend
    depends_on:
      - db
    deploy:
      replicas: 1
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 1
      labels: [APP=VOTING]
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 3
        window: 120s
      placement:
        constraints: [node.role = = manager]

  visualizer:
    image: dockersamples/visualizer:stable
    ports:
      - "8080:8080"
    stop_grace_period: 1m30s
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    deploy:
      placement:
        constraints: [node.role = = manager]

networks:
  frontend:
  backend:

volumes:
  db-data:
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In this sample, the top-level structure consists of version, Services, Networks, Volumes, and so on. This is not drastically different from version 2.

In the Services section, you can define several services, each of which typically runs a container, that constitute an overall stack of facilities, or cluster of services.

Generally we arrange a bunch of miscellaneous things, such as a bunch of microservices, into a service stack, so that they are served as a whole, so as not to expose the details, but also to enhance the architectural design flexibility and scale the entire service stack (rather than dealing with a large number of microservices).

Formatting manual –`service`

The following is a chapter structure of the reference manual. We list the instructions for service orchestration in alphabetical order, such as ports, Volumes, CMD, entry, and so on.

`build`

This option is used to build.

Build can be a path string pointing to the build context, for example:

version: "3.7"
services:
  webapp:
    build: ./dir
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Or it could be a more detailed definition. This includes the path specified by the context item, as well as the optional dockerFile and the build parameter args:

version: "3.7"
services:
  webapp:
    build:
      context: ./dir
      dockerfile: Dockerfile-alternate
      args:
        buildno: 1
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If you specify an image as well as a build, the result of the build will be marked with the appropriate name, just as docker build-t container-name:tag dir does:

    build: "./dir"
    image: "Company/webapp: v1.1.9"
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With YAML, a safe way to avoid ambiguity is to enclose strings in quotes.

In the example above, the build context is found in the./dir folder (the default is to find the Dockerfile), the build is completed, and it is marked with the company/ WebApp name and v1.1.9 Tag.

`context`

This can be a folder containing a Dockerfile or a URL pointing to a Git Repository.

If a relative path is specified, it is relative to the docker-comemage.yml file. This path is also passed to the Docker Daemon for building.

Docker-compose initiates the build action and marks the build result (by image name), and then uses it by the corresponding name.

`dockerfile`

You can specify a different file name than the default Dockerfile for the build. Note that you must also specify a path to the context:

    build:
      context: .
      dockerfile: Dockerfile-alternate
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`args`

Specify build parameters. This usually refers to parameters used at build time (see ARG in Dockerfile).

Here’s a quick overview:

First, specify parameters in Dockerfile:

ARG buildno
ARG gitcommithash

RUN echo "Build number: $buildno"
RUN echo "Based on commit: $gitcommithash"
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Then specify the actual value of the build argument (either a Map or an array is fine) :

  build:
    context: .
    args:
      buildno: 1
      gitcommithash: cdc3b19
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Or:

build:
  context: .
  args:
    - buildno=1
    - gitcommithash=cdc3b19
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NOTE: In a Dockerfile, if you specify an ARG before a FROM, the ARG is invalid for subsequent FROM closures.

Multiple FROM cuts out multiple constructed closures.

For the ARG to be valid in every FROM closure, you need to specify it in every closure.

There is a more detailed discussion in Understand how ARGS and FROM interact.

You can skip specifying build parameters. At this point, the actual value of this parameter depends on the build-time runtime environment.

  args:
    - buildno
    - gitcommithash
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NOTE: YAML boilers (true, false, yes, no, on, off) must be enclosed in quotes for docker-compose to handle correctly.

`cache_from`

Since v3.2

Specifies a list of images for caching resolution.

build:
  context: .
  cache_from:
    - alpine:latest
    - Corp/web_app: 3.14
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`labels`

Since v3.3

Add metadata labels, either an array or a dictionary, to the built image.

We recommend using the reverse DNS annotated prefix to prevent your tag from colliding with the user’s tag:

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

# anothor example
build:
  context: .
  labels:
    - "com.example.description=Accounting webapp"
    - "com.example.department=Finance"
    - "com.example.label-with-empty-value"
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`shm_size`

Since v3.5

Set the /dev/shm partition size for the build container. The integer format is expressed in bytes, but a string value can also be used:

build:
  context: .
  shm_size: '2gb'

build:
  context: .
  shm_size: 10000000
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`target`

Since v3.4

Build definitions and specific stages in dockerfiles, see multi-stage Build docs:

build:
  context: .
  target: prod
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Multiple builds are typically used for CI/CD.

Step 0 can be named as builder, for example, is responsible for compiling from source to the target file, while step 1 0 from step out the target file for deployment package, and produce the final container mirror, then step 0 layer is abandoned, the middle layer will not appear in the final container mirror, effectively reduce the size of the final container mirror, And this result is also semantically and logically self-consistent.
FROM Golang: 1.7.3 AS builder
WORKDIR /go/src/github.com/alexellis/href-counter/
RUN go get -d -v golang.org/x/net/html  
COPY app.go    .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .

FROM alpine:latest  
RUN apk --no-cache add ca-certificates
WORKDIR /root/
COPY --from=builder /go/src/github.com/alexellis/href-counter/app .
CMD ["./app"]  
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

`cap_add`.`cap_drop`

Add or remove Linux capabilities for containers. For a complete listing, see Man 7 Capabilities.

cap_add:
  - ALL

cap_drop:
  - NET_ADMIN
  - SYS_ADMIN
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NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

The Linux capability mechanism is largely a security mechanism. The specific meaning, usage and extension belong to the category of Linux operating system and will not be described again.

`cgroup_parent`

Optionally, specify a parent Cgroup for the container. Cgroup is also one of the most important basic concepts in Linux containerization implementations.

cgroup_parent: m-executor-abcd
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NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

`command`

Override the default commands in the container.

command: bundle exec thin -p 3000
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Command can also be specified as a list. In fact, this is the preferred way, unambiguous and secure, and consistent with the format in dockerfile:

command: ["bundle", "exec". "thin". "-p". "3000"]
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configs

Provide specific access to Config for each service.

A config contains a set of configuration information that can be created in a variety of ways. Deployment of containers that reference these configurations can better address issues such as production environment parameters. On the other hand, sensitive information can be isolated into a secure area, reducing the possibility of leakage to some extent.

NOTE: The specified configuration must already exist or be defined in the top-level Configs configuration. Otherwise the deployment of the entire container stack will fail.

Two different syntax variant formats are supported. Refer to configS for more information.

The short format

Specify only the configuration name. The container can then access the configuration /

version: "3.7"
services:
  redis:
    image: redis:latest
    deploy:
      replicas: 1
    configs:
      - my_config
      - my_other_config
configs:
  my_config:
    file: ./my_config.txt
  my_other_config:
    external: true
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The example above defines references to my_config and my_other_config in the redis container service using a short format. Here my_config is specified as a host file./my_config.txt, and my_other_config is specified as an external (resource), which means that the corresponding resource is already defined in the Docker. It may be created by docker Config Create, or by another container stack deployment.

If the external resource is not found, the container stack deployment will fail and a config not found error will be thrown.

Note: The config definition is only supported in the Docker-compose format in V3.3 and later.

Long format

The long format provides more information about where a config can be found and how it can be used:

Source: configuration name
Target: The path to which the configuration will be mounted in the container. Defaults to / < source >
Uid & GID: Linux/Unix uid and GID with numeric values, 0 if not specified. Windows does not support it.
Mode: indicates the file permission in base 8. The default value is 0444.

Configurations are not writable because they are mounted on a temporary file system. So if you set write permission, this will be ignored.

The executable bit can be set.

The following example is similar to the short format example:

version: "3.7"
services:
  redis:
    image: redis:latest
    deploy:
      replicas: 1
    configs:
      - source: my_config
        target: /redis_config
        uid: '103'
        gid: '103'
        mode: 0440
configs:
  my_config:
    file: ./my_config.txt
  my_other_config:
    external: true
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In this case, the redis container service does not access my_other_config.

You can authorize a service to access multiple configurations, and you can mix long and short formats.

Defining a config (at the top level) does not imply that a service will be able to access it.

`container_name`

Specify a custom container name instead of docker-compose itself generating a default one.

container_name: my-web-container
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Since Docker container names must be unique, you cannot scale a service with a custom container name.

NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

`credential_spec`

Since v3.3

The gMSA (Group Managed Service Account) mode is supported from V3.8.

Configure credentials for managed service accounts. This option is only available for Windows container services. Only file://

or registry://

can be used for credential_spce.

When using file:, the referenced file must be placed under the CredentialSpec subdirectory of the Docker data folder (usually C: ProgramData Docker\). The following example will load credential information from C: ProgramData Docker CredentialSpecs my-credential-sp:

credential_spec:
  file: my-credential-spec.json
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When registry: is used, credential information will be read in from Windows Registry on the Docker Daemon host. A registry entry must be located at:

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization\Containers\CredentialSpecs
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The following example reads the value of the my-credential-spec registry key:

credential_spec:
  registry: my-credential-spec
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GMSA configuration example

When configuring gMSA credentials for a service, consider the following example:

version: "3.8"
services:
  myservice:
    image: myimage:latest
    credential_spec:
      config: my_credential_spec

configs:
  my_credentials_spec:
    file: ./my-credential-spec.json|
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`depends_on`

Represents dependencies between services. Service dependencies cause the following behavior:

docker-compose upStart services in order of dependency. In the following example,db 和 redisbeforewebBe started.
docker-compose up SERVICEAutomatically includedSERVICEThe dependency of. In the following example,docker-compose up webIt will start automaticallydb 和 redis.
docker-compose stopStop services in order of dependency. In the following example,webWill be precededdb 和 redisBe stopped.

A simple example is as follows:

version: "3.7"
services:
  web:
    build: .
    depends_on:
      - db
      - redis
  redis:
    image: redis
  db:
    image: postgres
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A few things to note when using Depends_on:

depends_onDoesn’t mean waitingdb 和 redisStart when readywebInstead, they start after they startweb. If you want to wait until the service is ready to be used, refer toControlling startup order.

Version 3 is no longer supportedconditionFormulated.

depends_onThe option is ignored when deployed to Swarm Mode.

See also debug a stack in swarm mode

`deploy`

Version 3 only.

Specify configurations related to deployment and runtime.

This will only affect swarm deployed to a docker stack deploy.

Docker-compose up and docker-compose run are ignored.

version: "3.7"
services:
  redis:
    image: redis:alpine
    deploy:
      replicas: 6
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure
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Several suboptions are available:

`endpoint_mode`

swarm.

Version 3.3 only.

Endpoint_mode: VIP-docker requests a virtual IP (VIP) for access for the service.

Docker automatically loads and balances requests between the client and the valid working nodes of the service. The client does not need to know how many nodes are available for the service, nor the IP address or port number of the service node.

This is the default.
Endpoint_mode: DNSRR – Uses the DNS round-robin (DNSRR) algorithm to discover services. Docker sets a DNS entry for the service and returns a list of IP addresses by service name during DNS resolution. The client therefore directly selects a specific endpoint for access.

version: "3.7"

services:
  wordpress:
    image: wordpress
    ports:
      - "8080:80"
    networks:
      - overlay
    deploy:
      mode: replicated
      replicas: 2
      endpoint_mode: vip

  mysql:
    image: mysql
    volumes:
       - db-data:/var/lib/mysql/data
    networks:
       - overlay
    deploy:
      mode: replicated
      replicas: 2
      endpoint_mode: dnsrr

volumes:
  db-data:

networks:
  overlay:
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The endpoint_mode option is similarly used as a swarm mode command-line option (see Docker service Create). For a quick list of docker swarm commands, check out swarm Mode CLI Commands.

To learn more about Swarm Mode’s network model and service discovery mechanism, see Configure Service Discovery.

`labels`

Specify a label for the service. These labels are only applied to the corresponding service and are not applied to the container or container instance of the service.

version: "3.7"
services:
  web:
    image: web
    deploy:
      labels:
        com.example.description: "This label will appear on the web service"
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To set labels for containers, specify labels for services outside deploy:

version: "3.7"
services:
  web:
    image: web
    labels:
      com.example.description: "This label will appear on all containers for the web service"
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`mode`

It can be global or replicated. Global means strictly a swarm node running a service, replicated means multiple container instances can be run. The default is replicated.

See Replicated and Global Services under swarm.

version: "3.7"
services:
  worker:
    image: dockersamples/examplevotingapp_worker
    deploy:
      mode: global
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`placement`

Specify aints and preferences.

See the documentation created by the Docker service for more information about constraints and [Preferences], including a complete description of the corresponding syntax, the types available, and so on.

version: "3.7"
services:
  db:
    image: postgres
    deploy:
      placement:
        constraints:
          - node.role = = manager
          - engine.labels.operatingsystem = = ubuntu 14.04
        preferences:
          - spread: node.labels.zone
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`replicas`

If the service is replicated, Replicas assigns it a number indicating how many container instances can run on a swarm node.

version: "3.7"
services:
  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 6
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`resources`

Configure resource constraints.

NOTE: For non-swarm mode, This entry replaces older resource constraint options (such as CPU_shares, CPU_quota, CPUSet, mem_limit, memSWAP_limit, Entries such as mem_swappiness in versions before version 3).

Upgrade version 2. X to upgrade version 3.

Each of these resource constraint entries has a single value, equivalent to the docker Service Create equivalent.

In the following example, the Redis service is constrained to not use more than 50M memory, 50% CPU usage for single core, and reserves 20M memory and 25% CPU usage as the baseline.

version: "3.7"
services:
  redis:
    image: redis:alpine
    deploy:
      resources:
        limits:
          cpus: '0.50'
          memory: 50M
        reservations:
          cpus: '0.25'
          memory: 20M
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The following topics describe the available options for service or container resource constraints in swarm scenarios.

Out Of Memory Exceptions (OOME)

You will get an Out Of Memory Exception (OOME) if you attempt to use more Memory than the system has in your service and container instances. At this point, container instances, or Docker Daemons, may be cleared by the kernel’s OOM manager.

To prevent this from happening, make sure your application uses memory efficiently and legally. For such risks, see Understand the Risks of Running out of Memory for further assessment tips.

`restart_policy`

Indicates how to restart a container instance when it exits. Replace the restart:

condition: can I do fornone.on-failure 或 any(the default isany)
delay: Wait time before trying to restart (default: 0). One should be specified for itduration.
max_attempts: How many times does the restart attempt have to be aborted. The default value is never give up.
window: Duration of waiting to determine whether a restart is successful. By default, success is considered immediately without waiting. One should be specified for itduration.

version: "3.7"
services:
  redis:
    image: redis:alpine
    deploy:
      restart_policy:
        condition: on-failure
        delay: 5s
        max_attempts: 3
        window: 120s
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`rollback_config`

Version 3.7 file format and up

How the service should be rolled back in the case of a rolling update failure:

parallelism: Number of containers to be rolled back at the same time. If set to 0, all containers are rolled back at the same time.
delay: Wait time for each container group to be rolled back (default: 0)
failure_action: An action that should be performed if a rollback fails. Can becontinue 或 pause(the default ispause)
monitor: Cycle at which the failed rollback status is updated to the monitor (ns|us|ms|s|m|hThe default for0s.
max_failure_ratio: Tolerable percentage of rollback failures (default: 0)
order: Rollback operation sequence. Can I do forstop-first 或 start-first(the default isstop-first)

`update_config`

Indicates how the service should be updated. This is useful when configured for rolling updates:

parallelism: The number of containers updated at the same time. If set to 0, all containers are rolled back at the same time.
delay: Wait time before each container group is updated (default: 0)
failure_action: Action that should be performed when an update fails. Can becontinue 或 pause(the default ispause)
monitor: Cycle at which failed update status is updated to the monitor (ns|us|ms|s|m|hThe default for0s.
max_failure_ratio: Tolerable percentage of updates that fail (default: 0)
order: Update operation sequence. Can I do forstop-first 或 start-first(the default isstop-first)

NOTE: Order only works in V3.4 and later.

version: "3.7"
services:
  vote:
    image: dockersamples/examplevotingapp_vote:before
    depends_on:
      - redis
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
        delay: 10s
        order: stop-first
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NOT SUPPORTED FOR `DOCKER STACK DEPLOY`

The following suboptions (supported by docker-compose UP and docker-compose run) are not supported in docker stack deploy:

build
cgroup_parent
container_name
devices
tmpfs
external_links
links
network_mode
restart
security_opt
sysctls
userns_mode

Tip: See the section on how to configure volumes for services, swarms, and docker-stack.yml files. Volumes are supported but to work with swarms and services, they must be configured as named volumes or associated with services that are constrained to nodes with access to the requisite volumes.

`devices`

List of devices to be mapped. The usage is the same as –device for the docker command.

devices:
  - "/dev/ttyUSB0:/dev/ttyUSB0"
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NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

`dns`

User-defined DNS server list. You can specify a single value or a list.

DNS: 8.8.8.8 DNS: -8.8.8.8-9.9.9.9Copy the code

`dns_search`

User-defined DNS search domain name. You can specify a single value or a list.

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

Overrides the default entryPoint value defined in dockerFile.

entrypoint: /code/entrypoint.sh
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Entry points can also be a list:

entrypoint:
    - php
    - -d
    - zend_extension=/usr/local/lib/php/extensions/no-debug-non-zts-20100525/xdebug.so
    - -d
    - memory_limit=-1
    - vendor/bin/phpunit
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NOTE: Setting an entryPoint not only overrides any entryPoint defaults in the Dockerfile, but also cleans up any CMD defaults in the Dockerfile. So CMD in Dockerfile will be ignored.

`env_file`

Imports environment variable values from the given file. It can be a single value or a list.

env_file: .env
env_file:
  - ./common.env
  - ./apps/web.env
  - /opt/secrets.env
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For docker-comement-f files, env_file’s path is relative to the folder where the FILE resides.

The environment variables declared in the environment will override the values introduced here.

Each line in the corresponding file should define an environment variable using the VAR=VAL format. A line starting with # is a comment line and is ignored as a blank line.

# Set Rails/Rack environment
RACK_ENV=development
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NOTE: If the service defines a build item, the environment variables defined by env_file are not visible during the build process. You can only use the build suboption args to define build-time environment variable values.

The value of VAL is used as is and cannot be modified. For example, if a value is surrounded by quotes, then the value’s representation also contains quotes.

The order of the environment variable files also needs to be noted. The variable values defined in the later environment variables file overwrite the old values defined earlier.

`environment`

Add environment variables. You can use an array or a dictionary. Any Booleans: true, false, yes, no, and so on must be quoted as string literals.

The value value of the key-only environment variable depends on the host environment of the Docker-compose runtime, which is useful to prevent sensitive information from leaking.

environment:
  RACK_ENV: development
  SHOW: 'true'
  SESSION_SECRET:
environment:
  - RACK_ENV=development
  - SHOW=true
  - SESSION_SECRET
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NOTE: If the service defines a build item, the environment variables defined by env_file are not visible during the build process. You can only use the build suboption args to define build-time environment variable values.

`expose`

Expose ports to linked services. These ports are not published to the host. Only internal ports can be specified to be used for exposure.

expose:
 - "3000"
 - "8000"
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`external_links`

Link containers started outside of docker-comemage.yml to the given service.

It has similar semantics to the legacy links option.

external_links:
 - redis_1
 - project_db_1:mysql
 - project_db_1:postgresql
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NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

A more recommended approach is to construct a subnet through networks for linking between containers.

`extra_hosts`

Add a host name mapping. These mappings will be added to /etc/hosts. This function is equivalent to the command line argument –add-host.

extra_hosts:
 - "Somehost: 162.242.195.82"
 - "Otherhost: 50.31.209.229"
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`healthcheck`

Since v2.1

Used to verify that a service is “healthy”. Refer to HEALTHCHECK Dockerfile instruction.

healthcheck:
  test: ["CMD", "curl". "-f". "http://localhost"]
  interval: 1m30s
  timeout: 10s
  retries: 3
  start_period: 40s
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Interval, timeout, and start_period should be specified as durations.

Note: start_period is only available in V3.4 and later.

Test must be a single string value or a list. If it is a list, the first item must be NONE, CMD, one of cmd-shells. If it is a string, it implicitly represents a CMD-shell prefix.

# Hit the local web app
test: ["CMD", "curl". "-f". "http://localhost"]
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As in the example above, but implicitly calling /bin/sh is equivalent to the following form.

test: ["CMD-SHELL", "curl -f http://localhost || exit 1"]
test: curl -f https://localhost || exit 1
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To disable any default health check directions specified in the image, use disable: true. This is equivalent to specifying test: [“NONE”].

healthcheck:
  disable: true
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`image`

Specify the name of the image.

image: redis
image: Ubuntu: 14.04
image: tutum/influxdb
image: example-registry.com:4000/postgresql
image: a4bc65fd
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If the image doesn’t exist on the host, Compose will try to pull it down unless you also specify a build item.

`init`

Since v3.7

Run an init process in the container and forward signals. Setting true enables this feature for the service.

version: "3.7"
services:
  web:
    image: alpine:latest
    init: true
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The default init process uses the binary execution file Tini, which is installed at /usr/libexec/docker-init on the daemon host if needed. You can also configure daemons to use a different binary through init-path, see Configuration Option.

`isolation`

Specify the isolation level/technology for a container. In Linux, only the default value is supported. On Windows, the acceptable values are default, process, and Hyperv.

`labels`

To add metadata labels to containers, see Docker Labels. You can specify an array or a dictionary for it.

We recommend that you use reverse DNS tagging to define your tags, which can effectively avoid tag name conflicts.

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"
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`links`

It’s already a legacy feature. It will be removed in the near future.

Link another service to this container. You can specify both the SERVICE name and the link ALIAS (SERVICE:ALIAS), or you can skip the link ALIAS.

web:
  links:
   - db
   - db:database
   - redis
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Services that are already linked in will be accessible by the host name (that is, the link ALIAS).

Links are not necessary for inter-service communication. By default, any service can access other services by service name. See Links topic in Networking in Compose.

A link also represents a dependency, but this is already a depends_on task, so the link is not necessary.

`logging`

Specify log forwarding configuration for the service.

logging:
  driver: syslog
  options:
    syslog-address: "TCP: / / 192.168.0.42:123"
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Driver specifies the driver name, which is equivalent to –log-driver. The default value is json-file.

driver: "json-file"
driver: "syslog"
driver: "none"
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Forward the available drives can reference docs.docker.com/config/cont…

Specify the options for the drive with option, as in –log-opt. For example, for syslog:

driver: "syslog"
options:
  syslog-address: "TCP: / / 192.168.0.42:123"
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The default log forwarding driver is json-file. You can specify the log cutting size and maximum number of log history files to keep:

version: "3.7"
services:
  some-service:
    image: some-service
    logging:
      driver: "json-file"
      options:
        max-size: "200k"
        max-file: "10"
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`network_mode`

Network model.

The value is the same as –network. However, the service:[Service name] mode is supported.

network_mode: "bridge"
network_mode: "host"
network_mode: "none"
network_mode: "service:[service name]"
network_mode: "container:[container name/id]"
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NOTE: These options are ignored when deploying a stack to Swarm Mode.

See also debug a stack in swarm mode

NOTE: network_mode: “host” cannot be mixed with links.

`networks`

The network to join. The target network is defined in the top-level networks TAB of docker-comemage. yml.

services:
  some-service:
    networks:
     - some-network
     - other-network
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ALIASES

Specify an alias (that is, hostname) for the service on the network. Other containers on the same network can use the service name or service alias to connect to the container instance of the service.

Since aliases are network-wide, the same service can have different aliases on different networks.

services:
  some-service:
    networks:
      some-network:
        aliases:
         - alias1
         - alias3
      other-network:
        aliases:
         - alias2
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A more complex and complete example:

version: "3.7"

services:
  web:
    image: "nginx:alpine"
    networks:
      - new

  worker:
    image: "my-worker-image:latest"
    networks:
      - legacy

  db:
    image: mysql
    networks:
      new:
        aliases:
          - database
      legacy:
        aliases:
          - mysql

networks:
  new:
  legacy:
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IPV4_ADDRESS, IPV6_ADDRESS

Specify a static IP address.

Notice In the corresponding top-level network configuration, an IPAM block must be configured for the subnet and the static IP address must meet the subnet definition.

If IPv6 addressing is desired, the enable_ipv6 option must be set, and you must use a version 2.x Compose file. IPv6 options do not currently work in swarm mode.

One example is:

version: "3.7"

services:
  app:
    image: nginx:alpine
    networks:
      app_net:
        ipv4_address: 172.16238.10.
        ipv6_address: 2001: : 3984-3989:10

networks:
  app_net:
    ipam:
      driver: default
      config:
        - subnet: "172.16.238.0/24"
        - subnet: "2001, 3984:3989: : / 64"
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`pid`

pid: "host"
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Set the PID mode for the service to use the host. This enables server processes within the container to share the PID address space with the host operating system level. This is a typical Linux/Unix operating system concept, so I won’t expand on it here. Such sharing enables secure IPC communication with the PID address space.

`ports`

Expose ports to the host machine.

Note: Port exposure is incompatible with network_mode: host.

The short format

You can specify both the HOST and CONTAINER port (HOST:CONTAINER) to complete the mapping, or you can specify only the CONTAINER port to automatically map to a temporary port (starting with 32768) for the same HOST port.

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"
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Long format

Verbose definitions are allowed:

ports:
  - target: 80
    published: 8080
    protocol: tcp
    mode: host
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It’s obvious, so I’ll skip the explanation.

NOTE: Long format only works in V3.2 and later.

`restart`

No is the default restart policy. No matter how the container exits or fails, it will not be restarted automatically.

Specifying always will restart the container in any case.

An on-failure policy allows the container to be restarted only when it fails to exit.

restart: "no"
restart: always
restart: on-failure
restart: unless-stopped
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NOTE: These options are ignored when deploying a stack to Swarm Mode. (Use restart_policy to do this.)

See also debug a stack in swarm mode

`secrets`

From each service configuration, grant access to the top-level Secrets defined entry. Supports both short and long formats.

The short format

The short format only specifies the name of the sensitive content. This enables the container to mount the corresponding content to the /run/secrets/

location and access it.

The following example uses the short format to give Redis access to my_secret and my_other_secret. The contents of my_secret are defined in./my_secret.txt, and my_other_secret is defined as an external resource, such as the docker secret create. If no corresponding external resource is found, the stack deployment will fail and throw a Secret Not Found error.

version: "3.7"
services:
  redis:
    image: redis:latest
    deploy:
      replicas: 1
    secrets:
      - my_secret
      - my_other_secret
secrets:
  my_secret:
    file: ./my_secret.txt
  my_other_secret:
    external: true
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Long format

The long format allows for a finer definition of how sensitive content is used within the stack container.

source: The name of the sensitive content defined in Docker.
target: Is mounted to the container/run/secrets/File name in. If not specified, it is usedsourceName.
uid & gid: UID and GID of the files mounted in the container. 0 if not specified. Invalid on Windows.
mode: Octal permissions for files mounted within the container. The default in Docker 1.13.1 is0000, but in newer versions0444. The mounted file is not writable. The execution bit can be set, but is generally meaningless.

Here’s an example:

version: "3.7"
services:
  redis:
    image: redis:latest
    deploy:
      replicas: 1
    secrets:
      - source: my_secret
        target: redis_secret
        uid: '103'
        gid: '103'
        mode: 0440
secrets:
  my_secret:
    file: ./my_secret.txt
  my_other_secret:
    external: true
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Long and short formats can be mixed if you are defining multiple sensitive content.

`security_opt`

Override the default label semantics for each container.

security_opt:
  - label:user:USER
  - label:role:ROLE
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This is usually associated with SecCOMP, which can be a lengthy topic related to security configuration, so I won’t expand on it here.

NOTE: These options are ignored when deploying a stack to Swarm Mode. (Use restart_policy to do this.)

See also debug a stack in swarm mode

stop_grace_period

Specifies a wait period after which the container will be forced to clear the corresponding process of the container instance (via the SIGKILL signal) if the container fails to block the SIGTERM signal (or any other signal defined by stop_signal) to shut itself down properly.

stop_grace_period: 1s
stop_grace_period: 1m30s
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By default, it will wait for 10 seconds.

`stop_signal`

Set an alternate signal to shut down the container instance normally. The SIGTERM signal is used by default.

stop_signal: SIGUSR1
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`sysctls`

Set the kernel parameters for the container. You can use an array or a dictionary.

sysctls:
  net.core.somaxconn: 1024
  net.ipv4.tcp_syncookies: 0
sysctls:
  - net.core.somaxconn=1024
  - net.ipv4.tcp_syncookies=0
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NOTE: These options are ignored when deploying a stack to Swarm Mode. (Use restart_policy to do this.)

See also debug a stack in swarm mode

`tmpfs`

since v2

Mount a temporary file system to the container. It can be a single value or a list.

tmpfs: /run
tmpfs:
  - /run
  - /tmp
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NOTE: These options are ignored when deploying a stack to Swarm Mode. (Use restart_policy to do this.)

See also debug a stack in swarm mode

Since v3.6

Mount a temporary file system to the container. The Size parameter specifies the Size in bytes of the file system Size. The default value is unlimited.

 - type: tmpfs
     target: /app
     tmpfs:
       size: 1000
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`ulimits`

Overrides the default Ulimits value specified in the container. You can specify an integer as a single limit limit or a mapping to represent the soft/hard limit limits respectively.

ulimits:
  nproc: 65535
  nofile:
    soft: 20000
    hard: 40000
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`userns_mode`

userns_mode: "host"
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Disable user namespaces. If the Docker Daemon is configured to run in a User namespace.

NOTE: These options are ignored when deploying a stack to Swarm Mode. (Use restart_policy to do this.)

See also debug a stack in swarm mode

`volumes`

Mount the host path or name the volume.

You can mount a host path to a service without having to define it in top-level volumes.

If you want to reuse a volume to multiple services, define it in your top-level Volumes and name it.

You can use named volumes in Services, Swarms, and Stack Files.

NOTE: Define a named volume in the top-level volumes and reference it in the volumes list for a service.

The earlier volumes_from is no longer used.

See Use Volumes and Volume Plugins.

The following example illustrates a named volume, my_data, being used for web services. On the Web, also use a host folder./static to mount inside the container; A host file is mounted in db to the corresponding file in the container, and another named volume dbData is used.

version: "3.7"
services:
  web:
    image: nginx:alpine
    volumes:
      - type: volume
        source: mydata
        target: /data
        volume:
          nocopy: true
      - type: bind
        source: ./static
        target: /opt/app/static

  db:
    image: postgres:latest
    volumes:
      - "/var/run/postgres/postgres.sock:/var/run/postgres/postgres.sock"
      - "dbdata:/var/lib/postgresql/data"

volumes:
  mydata:
  dbdata:
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The short format

You can use the HOST:CONTAINER format, or attach an access mode HOST:CONTAINER:ro.

You can mount relative paths in a host.

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
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Long format

The long format allows for finer control.

type: Indicates the mount typevolume.bind.tmpfs 和 npipe
source: Mount source location. This can be a host path, a volume name defined in top-level volumes, and so on. If mounttmpfsThis parameter is meaningless.
target: Mount point path inside the container.
read_only: Boolean value to set the writability of the volume.
bind: Configures the additional bind option.
- propagation: Propagation mode for BIND.
volume: Configures additional volume options
- nocopy: Boolean to disable data replication (by default, when a volume is first created, the contents of the container are copied to the volume)
tmpfs: Configures additional TMPFS options
- size: TMPFS capacity, in bytes.
consistency: Mount consistency requirements:consistentHosts and containers have the same view,cachedRead operations are buffered, the host view is the main,delegatedRead and write operations are buffered and the container view is the body.

version: "3.7"
services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
    volumes:
      - type: volume
        source: mydata
        target: /data
        volume:
          nocopy: true
      - type: bind
        source: ./static
        target: /opt/app/static

networks:
  webnet:

volumes:
  mydata:
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Long format is available after V3.2

VOLUMES FOR SERVICES, SWARMS, AND STACK FILES

When working in services, swarms, or docker-stack.yml scenarios, note that a service in swarm can be deployed to any node, and when the service is updated, it may not be on the original node.

When the specified volume does not exist, Docker automatically creates an anonymous volume for the referenced service. Anonymous volumes are non-persistent, so when the associated container instance exits and is removed, the anonymous volume is destroyed.

If you want to persist your data, use named volumes and choose the appropriate volume driver, which should be cross-host so that data can roam between hosts. Otherwise, you should set constraints on the service so that it will only be deployed to specific nodes on which the corresponding volume service is working correctly.

As an example, votingApp Sample in Docker Labs’ Docker-stack. yml file defines a DB service that runs PostgresQL. It uses a named volume db-data to persist database data. This volume is bound by swarm to run only on the manager node, so no problems are solved. Here is the source code:

version: "3.7"
services:
  db:
    image: Postgres: 9.4
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - backend
    deploy:
      placement:
        constraints: [node.role = = manager]
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CACHING OPTIONS FOR VOLUME MOUNTS (DOCKER DESKTOP FOR MAC)

In Docker 17.04 CE Edge and later versions (even 17.06CE Edge and Stable), you can configure consistency constraints on how volumes are synchronized between containers and hosts. These symbols include:

consistentExactly the same. The default policy is that hosts and containers have the same view.
cachedHost computer prevails. The read operation to the volume is buffered, the host view is the body,
delegatedContainer prevails. Read and write operations to volumes are buffered, and the container view is the body.

This is specially adapted for Docker Desktop for Mac. Due to what is known about osXFX’s file-sharing features, properly setting conformance flags can improve performance when accessing mounted volumes inside and outside the container.

Here is an example of a cached volume:

version: "3.7"
services:
  php:
    image: PHP: 7.1 - FPM
    ports:
      - "9000"
    volumes:
      - .:/var/www/project:cached
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In the case that all reads and writes are buffered, even if any changes occur in the container (which is often possible to write to a typical architecture such as PHP Website), they are not immediately visible to the host and the writes in the container will pile up.

To check whether a volume is consistent within or outside the container, see Performance Tuning for Volume mounts (Shared filesystems).

I couldn’t translate it exactly here because it would have been too long, and I haven’t been able to organize the language on the subject.

`domainname`.`hostname`.`ipc`.`mac_address`.`privileged`.`read_only`.`shm_size`.`stdin_open`.`tty`.`user`.`working_dir`

These configurations have a single value. Corresponds to the corresponding command line argument of docker run. Mac_address has been abandoned.

user: postgresql
working_dir: /code

domainname: foo.com
hostname: foo
ipc: host
mac_address: 02:42:ac:11:65:43

privileged: true


read_only: true
shm_size: 64M
stdin_open: true
tty: true
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Duration specified

Some configuration options, such as interval or timeout (both suboptions of Check), accept a string-style value for a time period or period. They should have this format:

2.5s
10s
1m30s
2h32m
5h34m56s
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Suffixes that can be appended to numeric values are us, ms, S, m, and h.

The meaning is self-evident.

Specifying byte values

Some configuration options, such as the build suboption shm_size, accept a string-delimited capacity size parameter value. They should have this format:

2b
1024kb
2048k
300m
1gb
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Valid suffix units include b, k, m, and g. In addition, KB, MB and GB are also legal. Pure decimal values are not legal.

Volume formatting manual –`volumes`

The top-level volumes section can declare and create named volumes (without using volume_from) that can be referenced in the Volumes section of the Service section. So we can reuse them, even across multiple services. The Docker volume subcommand of the docker command has more reference information.

You can also refer to Use volumes and Volume Plugins for Volume usage.

Here is an example that contains two services. The database’s data store folder is shared between the two services, so the database can use the storage folder, and the backup service can also manipulate it to complete the backup task:

version: "3.7"

services:
  db:
    image: db
    volumes:
      - data-volume:/var/lib/db
  backup:
    image: backup-service
    volumes:
      - data-volume:/var/lib/backup/data

volumes:
  data-volume:
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The entries under the top-level Volumes section can be empty without specifying details, so the default volume driver will be applied (usually the local volume driver).

But you can also customize it with the following parameters:

`driver`

Specifies which volume driver will be used. In general, the default value will be local. If the volume driver is invalid or not working, the Docker Engine will return an error when docker-compose is up.

driver: foobar
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`driver_opts`

Optionally specify a set of key-value pair parameters that will be passed to the volume driver. So these parameter sets are specific to the volume driver, please refer to the volume driver documentation.

volumes:
  example:
    driver_opts:
      type: "nfs"
      o: "Addr = 10.40.0.199 nolock, soft, rw." "
      device: ":/docker/example"
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`external`

If set to true, the corresponding volume is ready to be created outside of the compose orchestration file. Docker-compse Up will not attempt to create the volume and will return an error if the volume does not already exist.

For V3.3 and lower versions of the compose format, external cannot be used in combination with other volume configuration parameters, such as driver, Driver_opts, labels, and so on. However, this restriction is no longer applicable to V3.4 and later.

In the following example, Compose looks for an external volume named data and mounts it to the DB service instead of trying to create a new volume named [projectName]_data.

version: "3.7"

services:
  db:
    image: postgres
    volumes:
      - data:/var/lib/postgresql/data

volumes:
  data:
    external: true
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External. name has been deprecated in v3.4+, after which name is used directly.

You can also specify a separate volume name (in this case, data is considered to be the volume alias when the volume is referenced in the current orchestration file) :

volumes:
  data:
    external:
      name: actual-name-of-volume
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External volumes are always created with docker stack deploy

When docker Stack deploy is deployed into Swarm, external volumes are always created automatically if they don’t exist. For further information, see Moby/Moby #29976,

`labels`

Use Docker Labels to add metadata to containers. It can be array format or dictionary format.

We recommend that you use reverse DNS tagging to prefix your metadata table keys with reverse domain names to avoid potential collisions with other applications’ table keys of the same name:

labels:
  com.example.description: "Database volume"
  com.example.department: "IT/Ops"
  com.example.label-with-empty-value: ""
labels:
  - "com.example.description=Database volume"
  - "com.example.department=IT/Ops"
  - "com.example.label-with-empty-value"
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`name`

Since v3.4 +

Specify a custom name for the volume. The value of the name can be used to resolve volumes with special character names. Note that this value is used as is, and the quotes are not ignored or prefixed with the stack name.

version: "3.7"
volumes:
  data:
    name: my-app-data
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Name can be combined with external:

version: "3.7"
volumes:
  data:
    external: true
    name: my-app-data
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Web Formatting Manual –`networks`

Top-level section Networks allows you to configure the network you want to create and use (the Compose Intranet).

For a complete description of using Docker network environment features in Compose, and all network driver options, see the Networking Guide.
For Docker Labs’ network-related coaching use cases, read up on Designing Scalable, Portable Docker Container Networks.

`driver`

Specify the driver for the network.

The default driver is specified by the startup parameter of the Docker Engine. Typically, the startup parameters are built in to use the Bridge driver on a single-node host and the overlay driver in Swarm Mode.

If the driver is not available, Docker Engine will return an error.

driver: overlay
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bridge

By default Docker uses the Bridge driver on each host node. For information on how Bridge networking works, see Docker Labs’ network-related tutorial use case: Bridge Networking.

overlay

The overlay driver builds a named subnet between multiple Swarm Mode nodes, which is a virtual network across hosts.

inswarm modeHow to establishoverlayThe network allows services to work correctly across hosts, please refer toDocker LabsNetwork-related coaching use cases:Overlay networking and service discovery.
If you want to dig deeperoverlayIs how to complete the virtual network construction across the host and how the message flow, can refer toOverlay Driver Network Architecture.

host or none

Use the host network stack, or not use the network.

This is equivalent to the command-line arguments –net=host and –net= None.

These two drivers and network models can only be used in the Docker Stack. If you are using docker compose directives, use network_mode to specify them.

If you want to use a particular network on a common build, use [network] as mentioned in the second yaml file example.

With built-in network models such as host and None, there are a few syntax caveats: If you define an external network with a name like Host or None (note that you don’t need to actually create them, as both are part of the Docker built-in network model), then you’ll need to use Hostnet or Nonet when referencing them in the Compose orchestration file, as in:

version: "3.7"
services:
  web:
    networks:
      hostnet: {}

networks:
  hostnet:
    external: true
    name: host

---
services:
  web:
    .
    build:
      .
      network: host
      context: .
      .
services:
  web:
    .
    networks:
      nonet: {}

networks:
  nonet:
    external: true
    name: none
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`driver_opts`

Specifies a set of options represented by a set of key-value pairs to pass to the network driver. They are driver-specific, so the specific parameters available should refer to the corresponding driver documentation.

driver_opts:
  foo: "bar"
  baz: 1
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`attachable`

Since v3.2 +

Can only be used in driver: Overlay scenarios.

If set to true, standalone containers can also be attached to the network. If standalone container instances are attached to an overlay network, services in the container and individual container instances can communicate with each other. Note that you can even attach container instances from other Docker daemons to this Overlay network.

networks:
  mynet1:
    driver: overlay
    attachable: true
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`enable_ipv6`

Enable IPv6 on the network/subnet.

Not supported in V3 +.

Enable_ipv6 requires you to use v2 format and cannot be used in Swarm Mode.

`ipam`

User-defined IPAM configuration. Each sub-configuration is an optional parameter.

driver: Customizes the IPAM driver without using the default value
config: A list of one to more configuration blocks. Each configuration block has the following sub-parameters:
- subnet: Subnet definition in CIDR format to delimit a network segment.

A complete example:

ipam:
  driver: default
  config:
    - subnet: 172.28. 0. 0/ 16
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NOTE: Additional IPAM such as gateway is only available in V2.

`internal`

By default, Docker is also connected to a bridge network to provide external connectivity. If you want to create an external overlay network, set this option to true.

`labels`

Use Docker Labels to add metadata to containers. It can be array format or dictionary format.

We recommend that you use reverse DNS tagging to prefix your metadata table keys with reverse domain names to avoid potential collisions with other applications’ table keys of the same name:

labels:
  com.example.description: "Financial transaction network"
  com.example.department: "Finance"
  com.example.label-with-empty-value: ""
labels:
  - "com.example.description=Financial transaction network"
  - "com.example.department=Finance"
  - "com.example.label-with-empty-value"
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`external`

If set to true, the network is created and managed outside of the Compose orchestration file. Dockercompose Up will not attempt to create it and will return an error if the network does not exist.

For v3.3 and later formats, external cannot be used with driver, Driver_opts, IPam, internal, etc. This restriction was removed after V3.4 +.

In the following example, proxy is a gateway to the outside world, and Compose will look for an outside external network created by docker Network Create Outside. Instead of trying to automatically create a new network called [projectName]_outside:

version: "3.7"

services:
  proxy:
    build: ./proxy
    networks:
      - outside
      - default
  app:
    build: ./app
    networks:
      - default

networks:
  outside:
    external: true
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External. name is deprecated in V3.5 and later, please use name instead.

You can also specify a separate network name to be referenced in the Compose orchestration file.

`name`

Since v3.5

Set a custom name for the network. The value of the name can be used to resolve volumes with special character names. Note that this value is used as is, and the quotes are not ignored or prefixed with the stack name.

version: "3.7"
networks:
  network1:
    name: my-app-net
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Name can be used with external:

version: "3.7"
networks:
  network1:
    external: true
    name: my-app-net
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Configuration item Formatting manual –`configs`

A top-level configS section declaration defines a configuration item or reference that can be authorized for use by an in-stack service. The source of the configuration item can be file or external.

file: The contents of the configuration item are in a host file.
external: If the value is set totrue“, indicating that the configuration item is already created. Docker will not attempt to build it, but will generate one if it doesn’t existconfig not foundError.
name: The name of the configuration item in the Docker. The value of the name can be used to resolve volumes with special character names. Note that this value is used as is, and the quotes are not ignored or prefixed with the stack name.

In the following example, my_first_config is automatically created and named

_my_first_config when deployed as part of the stack, while my_second_config already exists.

configs:
  my_first_config:
    file: ./config_data
  my_second_config:
    external: true
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The other variation is in the case of an external configuration item with a name definition, which can be referenced and used in Compose as redis_config:

configs:
  my_first_config:
    file: ./config_data
  my_second_config:
    external:
      name: redis_config
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You still need to declare configs sections within the stack for each service to gain access to configuration items, see Grant Access to the config.

Sensitive information item Formatting manual –`secrets`

The top-level secrets chapter declaration defines a sensitive information item, or its reference, that can be authorized for use by the stack service. The source of sensitive information items can be file or external.

fileThe contents of sensitive information items are in a host file.
external: If the value is set totrue, indicating that the sensitive information item is already created. Docker will not attempt to build it, but will generate one if it doesn’t existsecret not foundError.
name: The name of the sensitive information item in the Docker. The value of the name can be used to resolve volumes with special character names. Note that this value is used as is, and the quotes are not ignored or prefixed with the stack name.

In the following example, my_first_secret is automatically created and named

_my_first_secret when deployed as part of the stack, while my_second_secret already exists.

secrets:
  my_first_secret:
    file: ./secret_data
  my_second_secret:
    external: true
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Another variation is in the case of an external configuration item with a name definition, which can be referenced and used in Compose under the name redis_secret.

Compose File V3.5 and later

secrets:
  my_first_secret:
    file: ./secret_data
  my_second_secret:
    external: true
    name: redis_secret
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Compose File V3.4 and later

my_second_secret:
    external:
      name: redis_secret
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You still need to declare secret sections on the stack for each service to gain access to sensitive items, see Grant Access to the Secret.

Variable substitution

Environment variables can be used in the Compose orchestration file. When Docker-compose is running, compose extracts the variable values from the Shell environment variables. For example, if the operating system environment variable contains a definition of POSTGRES_VERSION=9.3, the following definition is used

db:
  image: "postgres:${POSTGRES_VERSION}"
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Is equivalent to

db:
  image: "Postgres: 9.3"
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If the environment variable does not exist or is an empty string, it is treated as an empty string.

You can use the.env file to set default values for environment variables. Compose will automatically look for the.env file in the current folder to get the value of the environment variable.

Env is only available in docker-compose up scenarios. It will not be used when docker stack is deployed.

Both syntax $VARIABLE and ${VARIABLE} are available. In addition, in v2.1 format, the following forms similar to Shell syntax can be used:

${VARIABLE:-default}Will returndefault, if the environment variableVARIABLEIs an empty string or not set.
${VARIABLE-default}Will returndefault, if the environment variableVARIABLEIf not set.

Similarly, the following syntax helps to specify an unambiguous value:

${VARIABLE:? err}An error message will be generatederr, if the environment variableVARIABLEEmpty or not set.
${VARIABLE? err}An error message will be generatederr, if the environment variableVARIABLEIf not set.

Other Shell syntax features are not supported, such as ${VARIABLE/foo/bar}.

If you need a dollar sign, use? . At this time? No longer participates in the interpretation of environment variable substitution. The following cases:

web:
  build: .
  command: "? VAR_NOT_INTERPOLATED_BY_COMPOSE"
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Compose will warn you if you forget this rule and use a single $character:

The VAR_NOT_INTERPOLATED_BY_COMPOSE is not set. Substituting an empty string.

Extension field

Since v3.4

By extending fields, choreography configuration fragments can be reused. They can be free-form, provided you define them at the top of the YAML document and their section names begin with x- :

version: '3.4'
x-custom:
  items:
    - a
    - b
  options:
    max-size: '12m'
  name: "custom"
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NOTE

Starting with V3.7 (for the 3.x series), or starting with V2.4 (for the 2.x series), extended fields can also be placed at the first level below the top-level section of services, Volumes, Networks, Configuration items, and sensitive information items.

Something like this:
version: '3.7'
services:
  redis:
    #...
  x-custom:
    items:
      - a
      - b
    options:
      max-size: '12m'
    name: "custom"
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By free-form, I mean that these definitions are not interpreted by Compose. However, when you insert references to them somewhere, they are expanded to the insertion point, and then the specific semantics are explained by Compose in conjunction with the context. This uses YAML anchors syntax.

For example, if you have multiple services that use the same logging option:

logging:
  options:
    max-size: '12m'
    max-file: '5'
  driver: json-file
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You can define it like this:

x-logging:
  &default-logging
  options:
    max-size: '12m'
    max-file: '5'
  driver: json-file

services:
  web:
    image: myapp/web:latest
    logging: *default-logging
  db:
    image: mysql:latest
    logging: *default-logging
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With YAML Merge Type syntax, you can also override certain suboptions when inserting extended field definitions. Such as:

version: '3.4'
x-volumes:
  &default-volume
  driver: foobar-storage

services:
  web:
    image: myapp/web:latest
    volumes: ["vol1", "vol2". "vol3"]
volumes:
  vol1: *default-volume
  vol2:
    << : *default-volume
    name: volume02
  vol3:
    << : *default-volume
    driver: default
    name: volume-local
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Compose document Reference

User guide
Installing Compose
Compose file versions and upgrading
Get started with Docker
Samples
Command line reference

The end of the

Original text: docs.docker.com/compose/com… .
Translation: github.com/hedzr/docke… .

origin

About the authorization

Choreography version 3

history

Choreograph file structures with examples

Formatting manual –service

build

context

dockerfile

args

cache_from

labels

shm_size

target

cap_add.cap_drop

cgroup_parent

command

configs

The short format

Long format

container_name

credential_spec

GMSA configuration example

depends_on

deploy

endpoint_mode

labels

mode

placement

replicas

resources

Out Of Memory Exceptions (OOME)

restart_policy

rollback_config

update_config

NOT SUPPORTED FOR DOCKER STACK DEPLOY

devices

dns

dns_search

entrypoint

env_file

environment

expose

external_links

extra_hosts

healthcheck

image

init

isolation

labels

links

logging

network_mode

networks

ALIASES

IPV4_ADDRESS, IPV6_ADDRESS

pid

ports

The short format

Long format

restart

secrets

The short format

Long format

security_opt

stop_grace_period

stop_signal

sysctls

tmpfs

ulimits

userns_mode

volumes

The short format

Long format

VOLUMES FOR SERVICES, SWARMS, AND STACK FILES

CACHING OPTIONS FOR VOLUME MOUNTS (DOCKER DESKTOP FOR MAC)

domainname.hostname.ipc.mac_address.privileged.read_only.shm_size.stdin_open.tty.user.working_dir

Duration specified

Specifying byte values

Formatting manual –`service`

`build`

`context`

`dockerfile`

`args`

`cache_from`

`labels`

`shm_size`

`target`

`cap_add`.`cap_drop`

`cgroup_parent`

`command`

`container_name`

`credential_spec`

`depends_on`

`deploy`

`endpoint_mode`

`labels`

`mode`

`placement`

`replicas`

`resources`

`restart_policy`

`rollback_config`

`update_config`

NOT SUPPORTED FOR `DOCKER STACK DEPLOY`

`devices`

`dns`

`dns_search`

`entrypoint`

`env_file`

`environment`

`expose`

`external_links`

`extra_hosts`

`healthcheck`

`image`

`init`

`isolation`

`labels`

`links`

`logging`

`network_mode`

`networks`

`pid`

`ports`

`restart`

`secrets`

`security_opt`

`stop_signal`

`sysctls`

`tmpfs`

`ulimits`

`userns_mode`

`volumes`

`domainname`.`hostname`.`ipc`.`mac_address`.`privileged`.`read_only`.`shm_size`.`stdin_open`.`tty`.`user`.`working_dir`

Volume formatting manual –`volumes`

`driver`

`driver_opts`

`external`

`labels`

`name`

Web Formatting Manual –`networks`

`driver`

`driver_opts`

`attachable`

`enable_ipv6`

`ipam`

`internal`

`labels`

`external`

`name`

Configuration item Formatting manual –`configs`

Sensitive information item Formatting manual –`secrets`