Use the Docker command line

docker

To list available commands, either run docker with no parameters or execute docker help:

$ docker
Usage: docker [OPTIONS] COMMAND [ARG...]
       docker [ --help | -v | --version ]

A self-sufficient runtime for containers.

Options:
      --config string      Location of client config files (default "/root/.docker")
  -c, --context string     Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set with "docker context use")
  -D, --debug              Enable debug mode
      --help               Print usage
  -H, --host value         Daemon socket(s) to connect to (default [])
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default "/root/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/root/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/root/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Commands:
    attach    Attach to a running container
    # […]

Description

Depending on your Docker system configuration, you may be required to preface each docker command with sudo. To avoid having to use sudo with the docker command, your system administrator can create a Unix group called docker and add users to it.

For more information about installing Docker or sudo configuration, refer to the installation instructions for your operating system.

Environment variables

The following list of environment variables are supported by the docker command line:

Because Docker is developed using Go, you can also use any environment variables used by the Go runtime. In particular, you may find these useful:

• HTTP_PROXY
• HTTPS_PROXY
• NO_PROXY

These Go environment variables are case-insensitive. See the Go specification for details on these variables.

Configuration files

By default, the Docker command line stores its configuration files in a directory called .docker within your $HOME directory.

Docker manages most of the files in the configuration directory and you should not modify them. However, you can modify the config.json file to control certain aspects of how the docker command behaves.

You can modify the docker command behavior using environment variables or command-line options. You can also use options within config.json to modify some of the same behavior. If an environment variable and the --config flag are set, the flag takes precedent over the environment variable. Command line options override environment variables and environment variables override properties you specify in a config.json file.

Change the .docker directory

To specify a different directory, use the DOCKER_CONFIG environment variable or the --config command line option. If both are specified, then the --config option overrides the DOCKER_CONFIG environment variable. The example below overrides the docker ps command using a config.json file located in the ~/testconfigs/ directory.

$ docker --config ~/testconfigs/ ps

This flag only applies to whatever command is being ran. For persistent configuration, you can set the DOCKER_CONFIG environment variable in your shell (e.g. ~/.profile or ~/.bashrc). The example below sets the new directory to be HOME/newdir/.docker.

$ echo export DOCKER_CONFIG=$HOME/newdir/.docker > ~/.profile

Docker CLI configuration file (config.json) properties

Use the Docker CLI configuration to customize settings for the docker CLI. The configuration file uses JSON formatting, and properties:

By default, configuration file is stored in ~/.docker/config.json. Refer to the change the .docker directory section to use a different location.

Warning

The configuration file and other files inside the ~/.docker configuration directory may contain sensitive information, such as authentication information for proxies or, depending on your credential store, credentials for your image registries. Review your configuration file’s content before sharing with others, and prevent committing the file to version control.

Customize the default output format for commands

These fields allow you to customize the default output format for some commands if no --format flag is provided.

Custom HTTP headers

The property HttpHeaders specifies a set of headers to include in all messages sent from the Docker client to the daemon. Docker does not try to interpret or understand these headers; it simply puts them into the messages. Docker does not allow these headers to change any headers it sets for itself.

Credential store options

The property credsStore specifies an external binary to serve as the default credential store. When this property is set, docker login will attempt to store credentials in the binary specified by docker-credential-<value> which is visible on $PATH. If this property is not set, credentials will be stored in the auths property of the config. For more information, see the Credentials store section in the docker login documentation

The property credHelpers specifies a set of credential helpers to use preferentially over credsStore or auths when storing and retrieving credentials for specific registries. If this property is set, the binary docker-credential-<value> will be used when storing or retrieving credentials for a specific registry. For more information, see the Credential helpers section in the docker login documentation

Orchestrator options for docker stacks

The property stackOrchestrator specifies the default orchestrator to use when running docker stack management commands. Valid values are "swarm", "kubernetes", and "all". This property can be overridden with the DOCKER_STACK_ORCHESTRATOR environment variable, or the --orchestrator flag.

Automatic proxy configuration for containers

The property proxies specifies proxy environment variables to be automatically set on containers, and set as --build-arg on containers used during docker build. A "default" set of proxies can be configured, and will be used for any docker daemon that the client connects to, or a configuration per host (docker daemon), for example, “https://docker-daemon1.example.com”. The following properties can be set for each environment:

These settings are used to configure proxy settings for containers only, and not used as proxy settings for the docker CLI or the dockerd daemon. Refer to the environment variables and HTTP/HTTPS proxy sections for configuring proxy settings for the cli and daemon.

Warning

Proxy settings may contain sensitive information (for example, if the proxy requires authentication). Environment variables are stored as plain text in the container’s configuration, and as such can be inspected through the remote API or committed to an image when using docker commit.

Default key-sequence to detach from containers

Once attached to a container, users detach from it and leave it running using the using CTRL-p CTRL-q key sequence. This detach key sequence is customizable using the detachKeys property. Specify a <sequence> value for the property. The format of the <sequence> is a comma-separated list of either a letter [a-Z], or the ctrl- combined with any of the following:

• a-z (a single lowercase alpha character )
• @ (at sign)
• [ (left bracket)
• \\ (two backward slashes)
• _ (underscore)
• ^ (caret)

Your customization applies to all containers started in with your Docker client. Users can override your custom or the default key sequence on a per-container basis. To do this, the user specifies the --detach-keys flag with the docker attach, docker exec, docker run or docker start command.

CLI Plugin options

The property plugins contains settings specific to CLI plugins. The key is the plugin name, while the value is a further map of options, which are specific to that plugin.

Sample configuration file

Following is a sample config.json file to illustrate the format used for various fields:

{
  "HttpHeaders": {
    "MyHeader": "MyValue"
  },
  "psFormat": "table {{.ID}}\\t{{.Image}}\\t{{.Command}}\\t{{.Labels}}",
  "imagesFormat": "table {{.ID}}\\t{{.Repository}}\\t{{.Tag}}\\t{{.CreatedAt}}",
  "pluginsFormat": "table {{.ID}}\t{{.Name}}\t{{.Enabled}}",
  "statsFormat": "table {{.Container}}\t{{.CPUPerc}}\t{{.MemUsage}}",
  "servicesFormat": "table {{.ID}}\t{{.Name}}\t{{.Mode}}",
  "secretFormat": "table {{.ID}}\t{{.Name}}\t{{.CreatedAt}}\t{{.UpdatedAt}}",
  "configFormat": "table {{.ID}}\t{{.Name}}\t{{.CreatedAt}}\t{{.UpdatedAt}}",
  "serviceInspectFormat": "pretty",
  "nodesFormat": "table {{.ID}}\t{{.Hostname}}\t{{.Availability}}",
  "detachKeys": "ctrl-e,e",
  "credsStore": "secretservice",
  "credHelpers": {
    "awesomereg.example.org": "hip-star",
    "unicorn.example.com": "vcbait"
  },
  "stackOrchestrator": "kubernetes",
  "plugins": {
    "plugin1": {
      "option": "value"
    },
    "plugin2": {
      "anotheroption": "anothervalue",
      "athirdoption": "athirdvalue"
    }
  },
  "proxies": {
    "default": {
      "httpProxy":  "http://user:pass@example.com:3128",
      "httpsProxy": "https://my-proxy.example.com:3129",
      "noProxy":    "intra.mycorp.example.com",
      "ftpProxy":   "http://user:pass@example.com:3128"
    },
    "https://manager1.mycorp.example.com:2377": {
      "httpProxy":  "http://user:pass@example.com:3128",
      "httpsProxy": "https://my-proxy.example.com:3129"
    }
  }
}

Experimental features

Experimental features provide early access to future product functionality. These features are intended for testing and feedback, and they may change between releases without warning or can be removed from a future release.

Notary

If using your own notary server and a self-signed certificate or an internal Certificate Authority, you need to place the certificate at tls/<registry_url>/ca.crt in your docker config directory.

Alternatively you can trust the certificate globally by adding it to your system’s list of root Certificate Authorities.

Examples

Display help text

To list the help on any command just execute the command, followed by the --help option.

$ docker run --help

Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

Run a command in a new container

Options:
      --add-host value             Add a custom host-to-IP mapping (host:ip) (default [])
  -a, --attach value               Attach to STDIN, STDOUT or STDERR (default [])
<...>

Option types

Single character command line options can be combined, so rather than typing docker run -i -t --name test busybox sh, you can write docker run -it --name test busybox sh.

Boolean

Boolean options take the form -d=false. The value you see in the help text is the default value which is set if you do not specify that flag. If you specify a Boolean flag without a value, this will set the flag to true, irrespective of the default value.

For example, running docker run -d will set the value to true, so your container will run in “detached” mode, in the background.

Options which default to true (e.g., docker build --rm=true) can only be set to the non-default value by explicitly setting them to false:

$ docker build --rm=false .

Multi

You can specify options like -a=[] multiple times in a single command line, for example in these commands:

$ docker run -a stdin -a stdout -i -t ubuntu /bin/bash

$ docker run -a stdin -a stdout -a stderr ubuntu /bin/ls

Sometimes, multiple options can call for a more complex value string as for -v:

$ docker run -v /host:/container example/mysql

Note

Do not use the -t and -a stderr options together due to limitations in the pty implementation. All stderr in pty mode simply goes to stdout.

Strings and Integers

Options like --name="" expect a string, and they can only be specified once. Options like -c=0 expect an integer, and they can only be specified once.