Customize the Docker extension

The Docker extension includes several Visual Studio Code tasks to control the behavior of Docker build and run, and form the basis of container startup for debugging.

The tasks allow for a great deal of control and customization. The final configuration is a combination of general defaults, platform-specific defaults (such as Node.js, Python, or .NET), and user input. User input takes precedence when it conflicts with defaults.

All common features of Visual Studio Code tasks (for example, grouping tasks into compound tasks) are supported by Docker extension tasks. For more information on common task features and properties, see the Visual Studio Code custom task documentation.

Docker build task

The docker-build task builds Docker images using the Docker command line (CLI). The task can be used by itself, or as part of a chain of tasks to run and/or debug an application within a Docker container.

The most important configuration settings for the docker-build task are dockerBuild and platform:

• The dockerBuild object specifies parameters for the Docker build command. Values specified by this object are applied directly to Docker build CLI invocation.
• The platform property is a hint that changes how the docker-build task determines Docker build defaults.

See property reference for full list of all task properties.

Platform support

While the docker-build task in tasks.json can be used to build any Docker image, the extension has explicit support (and simplified configuration) for Node.js, Python, and .NET Core.

Node.js (docker-build)

Minimal configuration using defaults

A Node.js based Docker image with no specific platform options can just set the platform property to node:

{
  "version": "2.0.0",
  "tasks": [
      {
          "label": "Build Node Image",
          "type": "docker-build",
          "platform": "node"
      }
  ]
}

Platform defaults

For Node.js Docker images, the docker-build task infers the following options:

Property	Inferred Value
dockerBuild.context	The same directory in which the package.json resides.
dockerBuild.dockerfile	The file Dockerfile in the same directory as the package.json resides.
dockerBuild.tag	The application's name property in package.json (if defined), else the base name of the folder in which package.json resides.

Python (docker-build)

Minimal configuration using defaults

A Python based Docker image with no specific platform options can just set the platform property to python:

{
  "tasks": [
      {
      "type": "docker-build",
      "label": "docker-build",
      "platform": "python"
    }
  ]
}

Platform defaults

For Python Docker images, the docker-build task infers the following options:

Property	Inferred Value
dockerBuild.context	The default context is the workspace folder.
dockerBuild.dockerfile	The default Dockerfile path will be in the root of the workspace folder.
dockerBuild.tag	The base name of the root workspace folder.
dockerBuild.pull	Defaults to true in order to pull new base images before building.

.NET (docker-build)

Minimal configuration using defaults

When you build a .NET-based Docker image, you can omit the platform property and just set the netCore object (platform is implicitly set to netcore when netCore object is present). Note that appProject is a required property:

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Build Node Image",
            "type": "docker-build",
            "netCore": {
                "appProject": "${workspaceFolder}/project.csproj"
            }
        }
    ]
}

Platform defaults

For .NET-based images, the docker-build task infers the following options:

Property	Inferred Value
dockerBuild.context	The root workspace folder.
dockerBuild.dockerfile	The file Dockerfile in the root workspace folder.
dockerBuild.tag	The base name of the root workspace folder.

Build task reference

Here are all properties available for configuring docker-build task. All properties are optional unless indicated otherwise.

Property	Description
dockerBuild	Options for controlling the docker build command executed (see below). Required unless platform is set.
platform	Determines the platform: .NET (netcore) or Node.js (node) and default settings for docker build command.
node	Determines options specific for Node.js projects (see below).
python	There are no object properties for Python in the docker-build task.
netCore	Determines options specific for .NET projects (see below).

dockerBuild object properties

Property	Description	docker build CLI Equivalent
context	The path to the Docker build context. Required, unless inferred from the platform.	PATH
dockerfile	The path to the Dockerfile. Required, unless inferred from the platform.	-f or --file
tag	The tag applied to the Docker image. Required, unless inferred from the platform.	-t or --tag
buildArgs	Build arguments applied to the command line. This is a list of key-value pairs.	--build-arg
labels	Labels added to the Docker image. This is a list of key-value pairs (a JSON object). In addition to labels specified here, a label com.microsoft.created-by, set to visual-studio-code is added to the image. This behavior can be turned off by setting includeDefaults property of the labels object to false.	--label
target	The target in the Dockerfile to build to.	--target
pull	Whether or not to pull new base images before building.	--pull
customOptions	Any extra parameters to add before the context argument. No attempt is made to resolve conflicts with other options or validate this option.	(any)

node object properties (docker-build task)

Property	Description	Default
package	The path to the package.json file associated with the Dockerfile and docker-build task.	The file package.json in the root workspace folder.

netCore object properties (docker-build task)

Property	Description
appProject	The .NET project file (.csproj, .fsproj, etc.) associated with the Dockerfile and docker-build task. Required always.

Docker run task

The docker-run task in tasks.json creates and starts a Docker container using the Docker command line (CLI). The task can be used by itself, or as part of a chain of tasks to debug an application within a Docker container.

The most important configuration settings for the docker-run task are dockerRun and platform:

• The dockerRun object specifies parameters for the Docker run command. Values specified by this object are applied directly to Docker run CLI invocation.
• The platform property is a hint that changes how the docker-run task determines Docker run defaults.

See property reference for full list of all task properties.

Docker run platform support

While the docker-run task can be used to run any Docker image, the extension has explicit support (and simplified configuration) for Node.js, Python, and .NET.

Node.js (docker-run)

Minimal configuration using defaults

A Node.js based Docker image with no specific platform options can just set the platform property to node.

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Run Node Image",
            "node": "docker-run",
            "platform": "node"
        }
    ]
}

Platform defaults

For Node.js-based Docker images, the docker-run task infers the following options:

Property	Inferred Value
dockerRun.command	Generated from the npm start script in the package.json (if it exists), else generated from the main property in the package.json.
dockerRun.containerName	Derived from the application package name.
dockerRun.image	The tag from a dependent docker-build task (if one exists) or derived from the application package name, itself derived from the name property within package.json or the base name of the folder in which it resides.

Python (docker-run)

When building a Python-based Docker image, you can omit the platform property and just set the python object (platform is implicitly set to python when python object is present)

Minimal configuration for Django Apps

{
    "type": "docker-run",
    "label": "docker-run: debug",
    "dependsOn": [
      "docker-build"
    ],
    "python": {
      "args": [
        "runserver",
        "0.0.0.0:8000",
        "--nothreading",
        "--noreload"
      ],
      "file": "path_to/manage.py"
    }
}

Minimal configuration for Flask Apps

{
    "type": "docker-run",
    "label": "docker-run: debug",
    "dependsOn": [
      "docker-build"
    ],
    "dockerRun": {
      "env": {
        "FLASK_APP": "path_to/flask_entry_point.py"
      }
    },
    "python": {
      "args": [
        "run",
        "--no-debugger",
        "--no-reload",
        "--host", "0.0.0.0",
        "--port", "5000"
      ],
      "module": "flask"
    }
}

Minimal configuration for General Apps

{
    "type": "docker-run",
    "label": "docker-run: debug",
    "dependsOn": [
      "docker-build"
    ],
    "python": {
      "file": "path_to/app_entry_point.py"
    }
}

Platform defaults

For Python-based Docker images, the docker-run task infers the following options:

Property	Inferred Value
dockerRun.command	Generated by the Python object and is called by the Python Debugger.
dockerRun.containerName	Derived from the base name of the root workspace folder.
dockerRun.image	The tag from a dependent docker-build task (if one exists) or derived from the base name of the root workspace folder.

.NET (docker-run)

Minimal configuration using defaults

When building a .NET-based Docker image, you can omit the platform property and just set the netCore object (platform is implicitly set to netcore when netCore object is present). Note that appProject is a required property:

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Run .NET Core Image",
            "type": "docker-run",
            "netCore": {
                "appProject": "${workspaceFolder}/project.csproj"
            }
        }
    ]
}

Platform defaults

For .NET-based images, the docker-run task infers the following options:

Property	Inferred Value
dockerRun.containerName	Derived from the base name of the root workspace folder.
dockerRun.env	Adds the following environment variables as required: ASPNETCORE_ENVIRONMENT, ASPNETCORE_URLS, and DOTNET_USE_POLLING_FILE_WATCHER.
dockerRun.image	The tag from a dependent docker-build task (if one exists) or derived from the base name of the root workspace folder.
dockerRun.os	Linux
dockerRun.volumes	Adds the following volumes as required: the local application folder, the source folder, the debugger folder, the NuGet package folder, and NuGet fallback folder.

Run task reference

Here are all properties available for configuring docker-run task. All properties are optional unless indicated otherwise.

Property	Description
dockerRun	Options for controlling the docker run command executed (see below). Required unless platform is set.
platform	Determines the platform: .NET (netcore) or Node.js (node) and default settings for docker run command.
node	For Node.js projects, this controls various options (see below).
python	For Python projects, this controls various options (see below).
netCore	For .NET projects, this controls various options (see below).

dockerRun object properties

Property	Description	CLI Equivalent
image	The name (tag) of the image to run. Required unless inferred from the platform.	IMAGE
command	The command to run upon starting the container. Required, unless inferred from the platform.	COMMAND [ARG...]
containerName	The name given to the started container. Required, unless inferred from the platform.	--name
env	Environment variables set in the container. This is a list of key-value pairs.	-e or --env
envFiles	This is a list of .env files.	--env-file
labels	Labels given to the started container. This is a list of key-value pairs.	--label
network	The name of the network to which the container will be connected.	--network
networkAlias	The network-scoped alias for the started container.	--network-alias
os	Default is Linux, the other option is Windows. The container operating system used.	N/A
ports	The ports to publish (map) from container to host. This is a list of objects (see below).	-p or --publish
portsPublishAll	Whether to publish all ports exposed by the Docker image. Defaults to true if no ports are explicitly published.	-P
extraHosts	The hosts to add to the container for DNS resolution. This is a list of objects (see below).	--add-host
volumes	The volumes to map into the started container. This is a list of objects (see below).	-v or --volume
remove	Whether or not to remove the container after it stops.	--rm
customOptions	Any extra parameters to add before the image argument. No attempt is made to resolve conflicts with other options or validate this option.	(any)

ports object properties

Property	Description	Default
containerPort	The port number bound on the container. Required.
hostPort	The port number bound on the host.	(randomly selected by Docker)
protocol	The protocol for the binding (tcp or udp).	tcp

extraHosts object properties

Property	Description
hostname	The hostname for DNS resolution. Required.
ip	The IP address associated with the above hostname. Required.

volumes object properties

Property	Description	Default
localPath	The path on the local machine that will be mapped. Required.
containerPath	The path in the container to which the local path will be mapped. Required.
permissions	Permissions the container has on the mapped path. Can be ro (read-only) or rw (read-write).	Container dependent.

node object properties (docker-run task)

Property	Description	Default
package	The path to the package.json file associated with the docker-run task.	The file package.json in the root workspace folder.
enableDebugging	Whether or not to enable debugging within the container.	false
inspectMode	Defines the initial interaction between the application and the debugger (default or break). The value default allows the application to run until the debugger attaches. The value break prevents the application from running until the debugger attaches.	default
inspectPort	The port on which debugging should occur.	9229

python object properties (docker-run task)

Property	Description	Default
args	Arguments passed to the Python app.	Platform dependent. Defaults of scaffolding shown above
debugPort	The port that the debugger will listen on.	5678
wait	Whether to wait for debugger to attach.	true
module	The Python module to run (only module or file should be chosen).
file	The Python file to run (only module or file should be chosen).

netCore object properties (docker-run task)

Property	Description
appProject	The .NET project file (.csproj, .fsproj, etc.) associated with docker-run task. Required.
configureSsl	Whether to configure ASP.NET Core SSL certificates and other settings to enable SSL on the service in the container.
enableDebugging	Whether to enable the started container for debugging. This will infer additional volume mappings and other options necessary for debugging.

Docker Compose task

The docker-compose task in tasks.json creates and starts Docker containers using the Docker Compose command line (CLI). The task can be used by itself, or as part of a chain of tasks to debug an application within a Docker container.

The most important configuration setting for the docker-compose task is dockerCompose:

• The dockerCompose object specifies parameters for the Docker Compose command. Values specified by this object are applied directly to Docker Compose CLI invocation.

See property reference for full list of all task properties.

Example configuration

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Run docker-compose up",
            "type": "docker-compose",
            "dockerCompose": {
                "up": {
                    "detached": true,
                    "build": true,
                    "services": [
                      "myservice"
                    ]
                },
                "files": [
                    "${workspaceFolder}/docker-compose.yml",
                    "${workspaceFolder}/docker-compose.debug.yml"
                ]
            }
        }
    ]
}

Compose task reference

Here are all properties available for configuring docker-compose task. All properties are optional unless indicated otherwise.

Property	Description
dockerCompose	Options for controlling the docker-compose command executed (see below). Required.

dockerCompose object properties

Property	Description	CLI Equivalent
up	Run a docker-compose up command. Either this or down must be specified, but not both.	docker-compose up
down	Run a docker-compose down command. Either this or up must be specified, but not both.	docker-compose down
files	The list of Docker Compose YAML files to use in the docker-compose command. If not specified, the Docker Compose CLI looks for docker-compose.yml and docker-compose.override.yml.	-f <file>
envFile	File of environment variables read in and applied to the containers.	--env-file <file>
projectName	Alternate project name to use when naming and labeling Docker objects. If using an alternate project name when composing up, the same project name must be specified when composing down.	--project-name <name>

up object properties

Property	Description	CLI Equivalent	Default
detached	Whether or not to run detached.	-d	true
build	Whether or not to build before running.	--build	true
scale	Number of instances of each service to run. This is a list of key-value pairs.	--scale SERVICE=NUM
services	A subset of the services to start. Cannot be combined with profiles.	[SERVICE...]	(all)
profiles	A subset of the profiles to start. Cannot be combined with services.	--profile <profile>	(all)
customOptions	Any extra parameters to add after the up argument. No attempt is made to resolve conflicts with other options or validate this option.	(any)

down object properties

Property	Description	CLI Equivalent	Default
removeImages	Whether to remove images, and which. all will remove all images used by any service, local will remove only images without a custom tag. Leaving this unset will remove no images.	--rmi
removeVolumes	Whether or not to remove named volumes.	-v	false
customOptions	Any extra parameters to add after the down argument. No attempt is made to resolve conflicts with other options or validate this option.	(any)

Command customization

The Docker extension executes a number of Docker CLI commands when you perform various operations, such as to build images, run containers, attach to containers, and view container logs. Some of these commands have a large number of optional arguments, often used in very specific scenarios. As an alternative to the above Visual Studio Code tasks, several commands can be customized when tasks are not in use.

For example, the tokens ${serviceList} and ${profileList} in the Compose Up command allows for easily starting a subset of the services within your Docker Compose YAML file(s).

For each of these customizable Docker commands, a configuration setting is available to set the template of what to execute. Alternatively, you can define multiple templates, optionally with a regular expression, which when matched, hints the context in which a template should be used. The templates support some tokens similar to launch.json and tasks.json, for example, ${workspaceFolder}.

Settings JSON schema

You have two options for configuring each of the templates (listed below). The first option is a single template that overrides the default behavior:

{
    "docker.commands.build": "docker build --rm -f \"${dockerfile}\" -t ${tag} \"${context}\""
}

The second option is multiple templates that will be chosen based on the match regular expression, as well as user input.

For example, three templates are shown in the following example:

{
    "docker.commands.build": [
        {
            "label": "Default build command",
            "template": "docker build --rm -f \"${dockerfile}\" -t ${tag} \"${context}\""
        },
        {
            "label": "Alpine-specific build command",
            "template": "docker build -p 1234:1234 -f \"${dockerfile}\" -t ${tag} \"${context}\"",
            "match": "alpine"
        }
    ]
}

Selection behavior

The command template chosen to execute is selected based on the following rules:

1. If no setting is configured, the default command template is chosen.
2. If only a single template is configured (the first example above), that template is chosen.
3. If multiple templates are configured:
   1. Constrained templates are checked. A constrained template has match. The match regular expression is compared against contextual hints--for example, image name, container name, etc.
   2. If multiple constrained templates apply, the user will be prompted to choose. If only one applies, the user will not be prompted.
   3. If there no applicable constrained templates, unconstrained templates are checked. An unconstrained template does not have match, and is therefore always applicable.
   4. If multiple unconstrained templates apply, the user will be prompted to choose. If only one applies, the user will not be prompted.

Docker Build

Configuration Setting	Default Value
docker.commands.build	${containerCommand} build --rm -f "${dockerfile}" -t ${tag} "${context}"

Supported tokens:

Token	Description
${containerCommand}	The CLI command / executable used to execute container commands.
${dockerfile}	The workspace-relative path of the selected Dockerfile.
${tag}	The value entered/confirmed by the user upon invoking the build command. If previously built, defaults to the previously entered value for that Dockerfile.
${context}	If set, the value of the docker.imageBuildContextPath configuration setting. Otherwise, the workspace-relative folder in which the Dockerfile resides.

Note: If the docker.commands.build setting does not contain the ${tag} token, the user will not be prompted to enter/confirm a tag.

Note: The match regular expression will be compared against the selected Dockerfile name and the workspace folder name.

Docker Run

Configuration Setting	Default Value
docker.commands.run	${containerCommand} run --rm -d ${exposedPorts} ${tag}
docker.commands.runInteractive	${containerCommand} run --rm -it ${exposedPorts} ${tag}

Supported tokens:

Token	Description
${containerCommand}	The CLI command / executable used to execute container commands.
${exposedPorts}	Generated from the list of exposed ports in the image (ultimately from the Dockerfile), where each exposed port is mapped to the same port on the local machine. For example, "EXPOSE 5000 5001" would generate "-p 5000:5000 -p 5001:5001".
${tag}	The full tag of the selected image.

Note: The match regular expression will be compared against the full tag of the selected image.

Docker Attach

Configuration Setting	Default Value
docker.commands.attach	${containerCommand} exec -it ${containerId} ${shellCommand}

Supported tokens:

Token	Description
${containerCommand}	The CLI command / executable used to execute container commands.
${containerId}	The ID of the container to attach to.
${shellCommand}	If bash is present in the container, it is substituted here, otherwise sh. In Windows containers, cmd is always used.

Note: The match regular expression will be compared against the container name and full tag of the container image.

Docker Logs

Configuration Setting	Default Value
docker.commands.logs	${containerCommand} logs -f ${containerId}

Supported tokens:

Token	Description
${containerCommand}	The CLI command / executable used to execute container commands.
${containerId}	The ID of the container to view the logs for.

Note: The match regular expression will be compared against the container name and full tag of the container image.

Docker Compose Up

Configuration Setting	Default Value
docker.commands.composeUp	${composeCommand} ${configurationFile} up ${detached} ${build}

Supported tokens:

Token	Description
${configurationFile}	Set to -f plus the workspace-relative path to the selected Docker Compose YAML file.
${detached}	Set to -d if the configuration setting docker.dockerComposeDetached is set to true. Otherwise, set to "".
${build}	Set to --build if the configuration setting docker.dockerComposeBuild is set to true. Otherwise, set to "".
${serviceList}	If specified, prompts for a subset of the services to start when the command is run.
${profileList}	If specified and the Docker Compose YAML file contains profiles, prompts for a subset of the profiles to start when the command is run.
${composeCommand}	Set to the value of the docker.composeCommand setting if set, otherwise the extension will try to automatically determine the command to use (docker compose or docker-compose).

Docker Compose Down

Configuration Setting	Default Value
docker.commands.composeDown	${composeCommand} ${configurationFile} down

Supported tokens:

Token	Description
${configurationFile}	Set to -f plus the workspace-relative path to the selected Docker Compose YAML file.
${composeCommand}	Set to the value of the docker.composeCommand setting if set, otherwise the extension will try to automatically determine the command to use (docker compose or docker-compose).

Additional supported tokens

In addition to the command-specific supported tokens, the following tokens are supported in all command templates:

Token	Description
${workspaceFolder}	The selected workspace folder path.
${config:some.setting.identifier}	The value of any configuration setting, as long as it is a string, number, or boolean. These setting identifiers can be arbitrarily defined and do not need to belong to Visual Studio Code or to any extension.
${env:Name}	The value of an environment variable.
${command:commandID}	The string return value of a command.