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Compose file reference

fig, composition, compose, docker

/compose/yml

/compose/compose-file-v3.md

Compose file version 3 reference

4

1

These topics describe version 3 of the Compose file format. This is the newest version.

For a Compose/Docker Engine compatibility matrix, and detailed guidelines on versions and upgrading, see Compose file versions and upgrading.

Compose file structure and examples

The topics on this reference page are organized alphabetically by top-level key to reflect the structure of the Compose file itself. Top-level keys that define a section in the configuration file such as build, deploy, depends_on, networks, and so on, are listed with the options that support them as sub-topics. This maps to the <key>: <option>: <value> indent structure of the Compose file.

The best way to quickly grok the layout and syntax of a Compose file is to read Get started with Docker Compose and to look at files for applications on GitHub. A good place to start is the version 3 Compose stack file we use for the voting app sample to illustrate multi-container apps, service definitions, swarm mode, the deploy key, and the docker stack deploy command. Click to show/hide the example file below. This file is fully explained in the voting app sample tutorial.

Example Compose file version 3


      version: "3"
      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:
</code></pre>
  </div>
</div>


Service configuration reference

The Compose file is a YAML file defining
services,
networks and
volumes.
The default path for a Compose file is ./docker-compose.yml.

Tip: You can use either a .yml or .yaml extension for this file. They both work.

A service definition contains configuration which will be applied to each
container started for that service, much like passing command-line parameters to
docker run. Likewise, network and volume definitions are analogous to
docker network create and docker volume create.
As with docker run, options specified in the Dockerfile (e.g., CMD,
EXPOSE, VOLUME, ENV) are respected by default - you don't need to
specify them again in docker-compose.yml.
You can use environment variables in configuration values with a Bash-like
${VARIABLE} syntax - see
variable substitution for full details.
This section contains a list of all configuration options supported by a service
definition in version 3.
build

Configuration options that are applied at build time.
build can be specified either as a string containing a path to the build
context, or an object with the path specified under context and
optionally dockerfile and args.
build: ./dir

build:
  context: ./dir
  dockerfile: Dockerfile-alternate
  args:
    buildno: 1

If you specify image as well as build, then Compose names the built image
with the webapp and optional tag specified in image:
build: ./dir
image: webapp:tag

This will result in an image named webapp and tagged tag, built from ./dir.

Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file. The docker stack command accepts only pre-built images.

context

Either a path to a directory containing a Dockerfile, or a url to a git repository.
When the value supplied is a relative path, it is interpreted as relative to the
location of the Compose file. This directory is also the build context that is
sent to the Docker daemon.
Compose will build and tag it with a generated name, and use that image thereafter.
build:
  context: ./dir

dockerfile

Alternate Dockerfile.
Compose will use an alternate file to build with. A build path must also be
specified.
build:
  context: .
  dockerfile: Dockerfile-alternate

args

Add build arguments, which are environment variables accessible only during the
build process.
First, specify the arguments in your Dockerfile:
ARG buildno
ARG password

RUN echo "Build number: $buildno"
RUN script-requiring-password.sh "$password"

Then specify the arguments under the build key. You can pass either a mapping
or a list:
build:
  context: .
  args:
    buildno: 1
    password: secret

build:
  context: .
  args:
    - buildno=1
    - password=secret

You can omit the value when specifying a build argument, in which case its value
at build time is the value in the environment where Compose is running.
args:
  - buildno
  - password


Note: YAML boolean values (true, false, yes, no, on, off) must
be enclosed in quotes, so that the parser interprets them as strings.

cache_from


Note: This option is new in v3.2

A list of images that the engine will use for cache resolution.
build:
  context: .
  cache_from:
    - alpine:latest
    - corp/web_app:3.14

cap_add, cap_drop

Add or drop container capabilities.
See man 7 capabilities for a full list.
cap_add:
  - ALL

cap_drop:
  - NET_ADMIN
  - SYS_ADMIN


Note: These options are ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

command

Override the default command.
command: bundle exec thin -p 3000

The command can also be a list, in a manner similar to
dockerfile:
command: [bundle, exec, thin, -p, 3000]

cgroup_parent

Specify an optional parent cgroup for the container.
cgroup_parent: m-executor-abcd


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

container_name

Specify a custom container name, rather than a generated default name.
container_name: my-web-container

Because Docker container names must be unique, you cannot scale a service
beyond 1 container if you have specified a custom name. Attempting to do so
results in an error.
deploy


Version 3 only.

Specify configuration related to the deployment and running of services. This
only takes effect when deploying to a swarm with
docker stack deploy, and is
ignored by docker-compose up and docker-compose run.
deploy:
  replicas: 6
  update_config:
    parallelism: 2
    delay: 10s
  restart_policy:
    condition: on-failure

Several sub-options are available:
mode

Either global (exactly one container per swarm node) or replicated (a
specified number of containers). The default is replicated.
mode: global

replicas

If the service is replicated (which is the default), specify the number of
containers that should be running at any given time.
mode: replicated
replicas: 6

placement

Specify placement constraints. For a full description of the syntax and
available types of constraints, see the
docker service create
documentation.
placement:
  constraints:
    - node.role == manager
    - engine.labels.operatingsystem == ubuntu 14.04

update_config

Configures how the service should be updated. Useful for configuring rolling
updates.

parallelism: The number of containers to update at a time.
delay: The time to wait between updating a group of containers.
failure_action: What to do if an update fails. One of continue or pause
(default: pause).
monitor: Duration after each task update to monitor for failure (ns|us|ms|s|m|h) (default 0s).
max_failure_ratio: Failure rate to tolerate during an update.

    update_config:
      parallelism: 2
      delay: 10s

resources

Configures resource constraints. This replaces the older resource constraint
options in Compose files prior to version 3 (cpu_shares, cpu_quota,
cpuset, mem_limit, memswap_limit, mem_swappiness).
Each of these is a single value, analogous to its
docker run counterpart.
resources:
  limits:
    cpus: '0.001'
    memory: 50M
  reservations:
    cpus: '0.0001'
    memory: 20M

restart_policy

Configures if and how to restart containers when they exit. Replaces
restart.

condition: One of none, on-failure or any (default: any).
delay: How long to wait between restart attempts, specified as a
duration (default: 0).
max_attempts: How many times to attempt to restart a container before giving
up (default: never give up).
window: How long to wait before deciding if a restart has succeeded,
specified as a duration (default:
decide immediately).

    restart_policy:
      condition: on-failure
      delay: 5s
      max_attempts: 3
      window: 120s

labels

Specify labels for the service. These labels will only be set on the service,
and not on any containers for the service.
version: "3"
services:
  web:
    image: web
    deploy:
      labels:
        com.example.description: "This label will appear on the web service"

To set labels on containers instead, use the labels key outside of deploy:
version: "3"
services:
  web:
    image: web
    labels:
      com.example.description: "This label will appear on all containers for the web service"

devices

List of device mappings.  Uses the same format as the --device docker
client create option.
devices:
  - "/dev/ttyUSB0:/dev/ttyUSB0"


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

depends_on

Express dependency between services, which has two effects:


docker-compose up will start services in dependency order. In the following
example, db and redis will be started before web.


docker-compose up SERVICE will automatically include SERVICE's
dependencies. In the following example, docker-compose up web will also
create and start db and redis.


Simple example:
version: '2'
services:
  web:
    build: .
    depends_on:
      - db
      - redis
  redis:
    image: redis
  db:
    image: postgres


Note: There are several things to be aware of when using depends_on:


depends_on will not wait for db and redis to be "ready" before
starting web - only until they have been started. If you need to wait
for a service to be ready, see Controlling startup order
for more on this problem and strategies for solving it.


Version 3 no longer supports the condition form of depends_on.


The depends_on option is ignored when
deploying a stack in swarm mode
with a version 3 Compose file.



dns

Custom DNS servers. Can be a single value or a list.
dns: 8.8.8.8
dns:
  - 8.8.8.8
  - 9.9.9.9


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

dns_search

Custom DNS search domains. Can be a single value or a list.
dns_search: example.com
dns_search:
  - dc1.example.com
  - dc2.example.com


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

tmpfs


Version 2 file format and up.

Mount a temporary file system inside the container. Can be a single value or a list.
tmpfs: /run
tmpfs:
  - /run
  - /tmp


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

entrypoint

Override the default entrypoint.
entrypoint: /code/entrypoint.sh

The entrypoint can also be a list, in a manner similar to
dockerfile:
entrypoint:
    - php
    - -d
    - zend_extension=/usr/local/lib/php/extensions/no-debug-non-zts-20100525/xdebug.so
    - -d
    - memory_limit=-1
    - vendor/bin/phpunit


Note: Setting entrypoint will both override any default entrypoint set
on the service's image with the ENTRYPOINT Dockerfile instruction, and
clear out any default command on the image - meaning that if there's a CMD
instruction in the Dockerfile, it will be ignored.

env_file

Add environment variables from a file. Can be a single value or a list.
If you have specified a Compose file with docker-compose -f FILE, paths in
env_file are relative to the directory that file is in.
Environment variables specified in environment override these values.
env_file: .env

env_file:
  - ./common.env
  - ./apps/web.env
  - /opt/secrets.env

Compose expects each line in an env file to be in VAR=VAL format. Lines
beginning with # (i.e. comments) are ignored, as are blank lines.
# Set Rails/Rack environment
RACK_ENV=development


Note: If your service specifies a build option, variables
defined in environment files will not be automatically visible during the
build. Use the args sub-option of build to define build-time
environment variables.

The value of VAL is used as is and not modified at all. For example if the value is
surrounded by quotes (as is often the case of shell variables), the quotes will be
included in the value passed to Compose.
environment

Add environment variables. You can use either an array or a dictionary. Any
boolean values; true, false, yes no, need to be enclosed in quotes to ensure
they are not converted to True or False by the YML parser.
Environment variables with only a key are resolved to their values on the
machine Compose is running on, which can be helpful for secret or host-specific values.
environment:
  RACK_ENV: development
  SHOW: 'true'
  SESSION_SECRET:

environment:
  - RACK_ENV=development
  - SHOW=true
  - SESSION_SECRET


Note: If your service specifies a build option, variables
defined in environment will not be automatically visible during the
build. Use the args sub-option of build to define build-time
environment variables.

expose

Expose ports without publishing them to the host machine - they'll only be
accessible to linked services. Only the internal port can be specified.
expose:
 - "3000"
 - "8000"

external_links

Link to containers started outside this docker-compose.yml or even outside of
Compose, especially for containers that provide shared or common services.
external_links follow semantics similar to the legacy option links when
specifying both the container name and the link alias (CONTAINER:ALIAS).
external_links:
 - redis_1
 - project_db_1:mysql
 - project_db_1:postgresql


Notes:


If you're using the version 2 or above file format, the
externally-created containers must be connected to at least one of the same
networks as the service which is linking to them. Starting with Version 2, links are a legacy option. We recommend using networks instead.


This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.



extra_hosts

Add hostname mappings. Use the same values as the docker client --add-host parameter.
extra_hosts:
 - "somehost:162.242.195.82"
 - "otherhost:50.31.209.229"

An entry with the ip address and hostname will be created in /etc/hosts inside containers for this service, e.g:
162.242.195.82  somehost
50.31.209.229   otherhost

healthcheck


Version 2.1 file format and up.

Configure a check that's run to determine whether or not containers for this
service are "healthy". See the docs for the
HEALTHCHECK Dockerfile instruction
for details on how healthchecks work.
healthcheck:
  test: ["CMD", "curl", "-f", "http://localhost"]
  interval: 1m30s
  timeout: 10s
  retries: 3

interval and timeout are specified as
durations.
test must be either a string or a list. If it's a list, the first item must be
either NONE, CMD or CMD-SHELL. If it's a string, it's equivalent to
specifying CMD-SHELL followed by that string.
# Hit the local web app
test: ["CMD", "curl", "-f", "http://localhost"]

# As above, but wrapped in /bin/sh. Both forms below are equivalent.
test: ["CMD-SHELL", "curl -f http://localhost && echo 'cool, it works'"]
test: curl -f https://localhost && echo 'cool, it works'

To disable any default healthcheck set by the image, you can use disable: true. This is equivalent to specifying test: ["NONE"].
healthcheck:
  disable: true

image

Specify the image to start the container from. Can either be a repository/tag or
a partial image ID.
image: redis
image: ubuntu:14.04
image: tutum/influxdb
image: example-registry.com:4000/postgresql
image: a4bc65fd

If the image does not exist, Compose attempts to pull it, unless you have also
specified build, in which case it builds it using the specified
options and tags it with the specified tag.
isolation

Specify a container’s isolation technology. On Linux, the only supported value
is default. On Windows, acceptable values are default, process and
hyperv. Refer to the
Docker Engine docs
for details.
labels

Add metadata to containers using Docker labels. You can use either an array or a dictionary.
It's recommended that you use reverse-DNS notation to prevent your labels from conflicting with those used by other software.
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"

links

Link to containers in another service. Either specify both the service name and
a link alias (SERVICE:ALIAS), or just the service name.
web:
  links:
   - db
   - db:database
   - redis

Containers for the linked service will be reachable at a hostname identical to
the alias, or the service name if no alias was specified.
Links also express dependency between services in the same way as
depends_on, so they determine the order of service startup.

Notes:


If you define both links and networks, services with
links between them must share at least one network in common in order to
communicate.


This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.



logging

Logging configuration for the service.
logging:
  driver: syslog
  options:
    syslog-address: "tcp://192.168.0.42:123"

The driver  name specifies a logging driver for the service's
containers, as with the --log-driver option for docker run
(documented here).
The default value is json-file.
driver: "json-file"
driver: "syslog"
driver: "none"


Note: Only the json-file and journald drivers make the logs available directly from
docker-compose up and docker-compose logs. Using any other driver will not
print any logs.

Specify logging options for the logging driver with the options key, as with the --log-opt option for docker run.
Logging options are key-value pairs. An example of syslog options:
driver: "syslog"
options:
  syslog-address: "tcp://192.168.0.42:123"

network_mode

Network mode. Use the same values as the docker client --net parameter, plus
the special form service:[service name].
network_mode: "bridge"
network_mode: "host"
network_mode: "none"
network_mode: "service:[service name]"
network_mode: "container:[container name/id]"


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

networks

Networks to join, referencing entries under the
top-level networks key.
services:
  some-service:
    networks:
     - some-network
     - other-network

aliases

Aliases (alternative hostnames) for this service on the network. Other containers on the same network can use either the service name or this alias to connect to one of the service's containers.
Since aliases is network-scoped, the same service can have different aliases on different networks.

Note: A network-wide alias can be shared by multiple containers, and even by multiple services. If it is, then exactly which container the name will resolve to is not guaranteed.

The general format is shown here.
services:
  some-service:
    networks:
      some-network:
        aliases:
         - alias1
         - alias3
      other-network:
        aliases:
         - alias2

In the example below, three services are provided (web, worker, and db), along with two networks (new and legacy). The db service is reachable at the hostname db or database on the new network, and at db or mysql on the legacy network.
version: '2'

services:
  web:
    build: ./web
    networks:
      - new

  worker:
    build: ./worker
    networks:
    - legacy

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

networks:
  new:
  legacy:

ipv4_address, ipv6_address

Specify a static IP address for containers for this service when joining the network.
The corresponding network configuration in the top-level networks section must have an ipam block with subnet configurations covering each static address. If IPv6 addressing is desired, the enable_ipv6 option must be set.
An example:
version: '2.1'

services:
  app:
    image: busybox
    command: ifconfig
    networks:
      app_net:
        ipv4_address: 172.16.238.10
        ipv6_address: 2001:3984:3989::10

networks:
  app_net:
    driver: bridge
    enable_ipv6: true
    ipam:
      driver: default
      config:
      -
        subnet: 172.16.238.0/24
      -
        subnet: 2001:3984:3989::/64

link_local_ips

Specify a list of link-local IPs. Link-local IPs are special IPs which belong
to a well known subnet and are purely managed by the operator, usually
dependent on the architecture where they are deployed. Therefore they are not
managed by docker (IPAM driver).
Example usage:
version: '2.1'
services:
  app:
    image: busybox
    command: top
    networks:
      app_net:
        link_local_ips:
          - 57.123.22.11
          - 57.123.22.13
networks:
  app_net:
    driver: bridge

pid

pid: "host"

Sets the PID mode to the host PID mode.  This turns on sharing between
container and the host operating system the PID address space.  Containers
launched with this flag will be able to access and manipulate other
containers in the bare-metal machine's namespace and vise-versa.
ports

Expose ports.
Short syntax

Either specify both ports (HOST:CONTAINER), or just the container
port (a random host port will be chosen).

Note: When mapping ports in the HOST:CONTAINER format, you may experience
erroneous results when using a container port lower than 60, because YAML will
parse numbers in the format xx:yy as sexagesimal (base 60). For this reason,
we recommend always explicitly specifying your port mappings as strings.

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"

Long syntax

The long form syntax allows the configuration of additional fields that can't be
expressed in the short form.

target: the publicly exposed port
published: the port inside the container
protocol: the port protocol (tcp or udp)
mode: host for publishing a host port on each node, or ingress for a swarm
mode port which will be load balanced.

ports:
  - target: 8080
    published: 80
    protocol: tcp
    mode: host



Note: The long syntax is new in v3.2

secrets

Grant access to secrets on a per-service basis using the per-service secrets
configuration. Two different syntax variants are supported.

Note: The secret must already exist or be
defined in the top-level secrets configuration
of this stack file, or stack deployment will fail.

Short syntax

The short syntax variant only specifies the secret name. This grants the
container access to the secret and mounts it at /run/secrets/<secret_name>
within the container. The source name and destination mountpoint are both set
to the secret name.

Warning: Due to a bug in Docker 1.13.1, using the short syntax currently
mounts the secret with permissions 000, which means secrets defined using
the short syntax are unreadable within the container if the command does not
run as the root user. The workaround is to use the long syntax instead if
you use Docker 1.13.1 and the secret must be read by a non-root user.

The following example uses the short syntax to grant the redis service
access to the my_secret and my_other_secret secrets. The value of
my_secret is set to the contents of the file ./my_secret.txt, and
my_other_secret is defined as an external resource, which means that it has
already been defined in Docker, either by running the docker secret create
command or by another stack deployment. If the external secret does not exist,
the stack deployment fails with a secret not found error.
version: "3.1"
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

Long syntax

The long syntax provides more granularity in how the secret is created within
the service's task containers.

source: The name of the secret as it exists in Docker.
target: The name of the file that will be mounted in /run/secrets/ in the
service's task containers. Defaults to source if not specified.
uid and gid: The numeric UID or GID which will own the file within
/run/secrets/ in the service's task containers. Both default to 0 if not
specified.
mode: The permissions for the file that will be mounted in /run/secrets/
in the service's task containers, in octal notation. For instance, 0444
represents world-readable. The default in Docker 1.13.1 is 0000, but will
be 0444 in the future. Secrets cannot be writable because they are mounted
in a temporary filesystem, so if you set the writable bit, it is ignored. The
executable bit can be set. If you aren't familiar with UNIX file permission
modes, you may find this
permissions calculator{: target="blank" class="" }
useful.

The following example sets name of the my_secret to redis_secret within the
container, sets the mode to 0440 (group-readable) and sets the user and group
to 103. The redis service does not have access to the my_other_secret
secret.
version: "3.1"
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

You can grant a service access to multiple secrets and you can mix long and
short syntax. Defining a secret does not imply granting a service access to it.
security_opt

Override the default labeling scheme for each container.
security_opt:
  - label:user:USER
  - label:role:ROLE


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

stop_grace_period

Specify how long to wait when attempting to stop a container if it doesn't
handle SIGTERM (or whatever stop signal has been specified with
stop_signal), before sending SIGKILL. Specified
as a duration.
stop_grace_period: 1s
stop_grace_period: 1m30s

By default, stop waits 10 seconds for the container to exit before sending
SIGKILL.
stop_signal

Sets an alternative signal to stop the container. By default stop uses
SIGTERM. Setting an alternative signal using stop_signal will cause
stop to send that signal instead.
stop_signal: SIGUSR1


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

sysctls

Kernel parameters to set in the container. You can use either 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


Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

ulimits

Override the default ulimits for a container. You can either specify a single
limit as an integer or soft/hard limits as a mapping.
ulimits:
  nproc: 65535
  nofile:
    soft: 20000
    hard: 40000

userns_mode

userns_mode: "host"

Disables the user namespace for this service, if Docker daemon is configured with user namespaces.
See dockerd for
more information.

Note: This option is ignored when
deploying a stack in swarm mode
with a (version 3) Compose file.

volumes


Note: The top-level
volumes option defines
a named volume and references it from each service's volumes list. This replaces volumes_from in earlier versions of the Compose file format.

Mount host paths or named volumes. Named volumes must be defined in the
top-level volumes key.
Short syntax

Optionally specify a path on the host machine
(HOST:CONTAINER), or an access mode (HOST:CONTAINER:ro).
You can mount a relative path on the host, which will expand relative to
the directory of the Compose configuration file being used. Relative paths
should always begin with . or ...
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

Long syntax

The long form syntax allows the configuration of additional fields that can't be
expressed in the short form.

type: the mount type volume or bind
source: the source of the mount, a path on the host for a bind mount, or the
name of a volume defined in the
top-level volumes key
target: the path in the container where the volume will be mounted
read_only: flag to set the volume as read-only
bind: configure additional bind options

propagation: the propagation mode used for the bind


volume: configure additional volume options

nocopy: flag to disable copying of data from a container when a volume is
created



volumes:
  - type: volume
    source: mydata
    target: /data
    volume:
      nocopy: true
  - type: bind
    source: ./static
    target: /opt/app/static

restart

no is the default restart policy, and it will not restart a container under any circumstance. When always is specified, the container always restarts. The on-failure policy restarts a container if the exit code indicates an on-failure error.
  - restart: no
  - restart: always
  - restart: on-failure


Note: The long syntax is new in v3.2

See Docker Volumes and
Volume Plugins for more information.
domainname, hostname, ipc, mac_address, privileged, read_only, shm_size, stdin_open, tty, user, working_dir

Each of these is a single value, analogous to its
docker run counterpart.
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

Specifying durations

Some configuration options, such as the interval and timeout sub-options for
healthcheck, accept a duration as a string in a
format that looks like this:
2.5s
10s
1m30s
2h32m
5h34m56s

The supported units are us, ms, s, m and h.
Volume configuration reference

While it is possible to declare volumes on the fly as part of the service
declaration, this section allows you to create named volumes that can be
reused across multiple services (without relying on volumes_from), and are
easily retrieved and inspected using the docker command line or API.
See the docker volume
subcommand documentation for more information.
Here's an example of a two-service setup where a database's data directory is
shared with another service as a volume so that it can be periodically backed
up:
version: "3"

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

volumes:
  data-volume:

An entry under the top-level volumes key can be empty, in which case it will
use the default driver configured by the Engine (in most cases, this is the
local driver). Optionally, you can configure it with the following keys:
driver

Specify which volume driver should be used for this volume. Defaults to whatever
driver the Docker Engine has been configured to use, which in most cases is
local. If the driver is not available, the Engine will return an error when
docker-compose up tries to create the volume.
 driver: foobar

driver_opts

Specify a list of options as key-value pairs to pass to the driver for this
volume. Those options are driver-dependent - consult the driver's
documentation for more information. Optional.
 driver_opts:
   foo: "bar"
   baz: 1

external

If set to true, specifies that this volume has been created outside of
Compose. docker-compose up will not attempt to create it, and will raise
an error if it doesn't exist.
external cannot be used in conjunction with other volume configuration keys
(driver, driver_opts).
In the example below, instead of attempting to create a volume called
[projectname]_data, Compose will look for an existing volume simply
called data and mount it into the db service's containers.
version: '2'

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

volumes:
  data:
    external: true

You can also specify the name of the volume separately from the name used to
refer to it within the Compose file:
volumes:
  data:
    external:
      name: actual-name-of-volume

labels

Add metadata to containers using
Docker labels. You can use either
an array or a dictionary.
It's recommended that you use reverse-DNS notation to prevent your labels from
conflicting with those used by other software.
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"

Network configuration reference

The top-level networks key lets you specify networks to be created.


For a full explanation of Compose's use of Docker networking features and all
network driver options, see the Networking guide.


For Docker Labs
tutorials on networking, start with Designing Scalable, Portable Docker
Container
Networks


driver

Specify which driver should be used for this network.
The default driver depends on how the Docker Engine you're using is configured,
but in most instances it will be bridge on a single host and overlay on a
Swarm.
The Docker Engine will return an error if the driver is not available.
driver: overlay

bridge

Docker defaults to using a bridge network on a single host. For examples of
how to work with bridge networks, see the Docker Labs tutorial on Bridge
networking.
overlay

The overlay driver creates a named network across multiple nodes in a
swarm.


For a working example of how to build and use an
overlay network with a service in swarm mode, see the Docker Labs tutorial on
Overlay networking and service
discovery.


For an in-depth look at how it works under the hood, see the
networking concepts lab on the Overlay Driver Network
Architecture.


driver_opts

Specify a list of options as key-value pairs to pass to the driver for this
network. Those options are driver-dependent - consult the driver's
documentation for more information. Optional.
  driver_opts:
    foo: "bar"
    baz: 1

enable_ipv6

Enable IPv6 networking on this network.
ipam

Specify custom IPAM config. This is an object with several properties, each of
which is optional:

driver: Custom IPAM driver, instead of the default.
config: A list with zero or more config blocks, each containing any of
the following keys:

subnet: Subnet in CIDR format that represents a network segment



A full example:
ipam:
  driver: default
  config:
    - subnet: 172.28.0.0/16


Note: Additional IPAM configurations, such as gateway, are only honored for version 2 at the moment.

internal

By default, Docker also connects a bridge network to it to provide external
connectivity. If you want to create an externally isolated overlay network,
you can set this option to true.
labels

Add metadata to containers using
Docker labels. You can use either
an array or a dictionary.
It's recommended that you use reverse-DNS notation to prevent your labels from
conflicting with those used by other software.
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"

external

If set to true, specifies that this network has been created outside of
Compose. docker-compose up will not attempt to create it, and will raise
an error if it doesn't exist.
external cannot be used in conjunction with other network configuration keys
(driver, driver_opts, ipam, internal).
In the example below, proxy is the gateway to the outside world. Instead of
attempting to create a network called [projectname]_outside, Compose will
look for an existing network simply called outside and connect the proxy
service's containers to it.
version: '2'

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

networks:
  outside:
    external: true

You can also specify the name of the network separately from the name used to
refer to it within the Compose file:
networks:
  outside:
    external:
      name: actual-name-of-network

secrets configuration reference

The top-level secrets declaration defines or references
secrets which can be granted to the services in this
stack. The source of the secret is either file or external.

file: The secret is created with the contents of the file at the specified
path.
external: If set to true, specifies that this secret has already been
created. Docker will not attempt to create it, and if it does not exist, a
secret not found error occurs.

In this example, my_first_secret will be created (as
<stack_name>_my_first_secret)when the stack is deployed,
and my_second_secret already exists in Docker.
secrets:
  my_first_secret:
    file: ./secret_data
  my_second_secret:
    external: true

You still need to grant access to the secrets to each service in the
stack.
Variable substitution

{% include content/compose-var-sub.md %}
Compose documentation


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

Files

index.md

Latest commit

History

index.md

File metadata and controls

Compose file structure and examples

Example Compose file version 3

Service configuration reference

build

context

dockerfile

args

cache_from

cap_add, cap_drop

command

cgroup_parent

container_name

deploy

mode

replicas

placement

update_config

resources

restart_policy

labels

devices

depends_on

dns

dns_search

tmpfs

entrypoint

env_file

environment

expose

external_links

extra_hosts

healthcheck

image

isolation

labels

links

logging

network_mode

networks

aliases

ipv4_address, ipv6_address

link_local_ips

pid

ports

Short syntax

Long syntax

secrets

Short syntax

Long syntax

security_opt

stop_grace_period

stop_signal

sysctls

ulimits

userns_mode

volumes

Short syntax

Long syntax

restart

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

Specifying durations

Volume configuration reference

driver

driver_opts

external

labels

Network configuration reference

driver

bridge

overlay

driver_opts

enable_ipv6

ipam

internal