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 Core), 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 Core (docker-build)

Minimal configuration using defaults

When you build a .NET Core-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 Core-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 Core (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 Core 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

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 Core 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.

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 Core.

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 Core (docker-run)

Minimal configuration using defaults

When building a .NET Core-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 Core-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 Core (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 Core 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

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 Core 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.

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. Many of these commands can be customized.

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 is a single template that overrides the default behavior:

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

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

For example, two 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. Templates containing a defined match property are examined first. The match regular expression is compared against the context--for example, image name, container name, etc. All matching templates are selected. More information on the matching context is available below.
    2. If no templates match the match property, all templates without a defined match property are selected.
    3. If no templates match the match property, and there are no templates without a defined match property, then the default command template is chosen.
    4. Any time that multiple templates are selected, the user will be prompted to choose between them on which to execute.

Docker Build

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

Supported tokens:

Token Description
${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 docker run --rm -d ${exposedPorts} ${tag}
docker.commands.runInteractive docker run --rm -it ${exposedPorts} ${tag}

Supported tokens:

Token Description
${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 docker exec -it ${containerId} ${shellCommand}

Supported tokens:

Token Description
${containerId} The ID of the container to attach to.
${shellCommand} The value of the docker.attachShellCommand.linuxContainer or docker.attachShellCommand.windowsContainer configuration setting, as appropriate.

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 docker logs -f ${containerId}

Supported tokens:

Token Description
${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 docker-compose ${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 "".

Docker Compose Down

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

Supported tokens:

Token Description
${configurationFile} Set to -f plus the workspace-relative path to the selected Docker Compose YAML file.

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.