How use the "docker help" command?

The "docker help" command allows you to learn how to use "docker" command. It has 3 levels of helps.

1. "docker help" - Top level help. It lists top level commands and options. For example:

fyicenter# docker help

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files (default "/root/.docker")
  -H, --host list          Daemon socket(s) to connect to
  -v, --version            Print version information and quit

Management Commands:
  app*        Docker App (Docker Inc., v0.9.1-beta3)
  builder     Manage builds
  buildx*     Build with BuildKit (Docker Inc., v0.5.1-docker)
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts
  image       Manage images
  ...

2. "docker help <command>" - Command level help. It lists sub-commands of a given top level command. For example:

fyicenter# docker help container

Usage:  docker container COMMAND

Manage containers

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  inspect     Display detailed information on one or more containers
  kill        Kill one or more running containers
  logs        Fetch the logs of a container
  ...

2. "docker help <command> <sub-command>" - Sub-command level help. It lists options of a given sub-command. For example:

fyicenter# docker help container exec

Usage:  docker container exec [OPTIONS] CONTAINER COMMAND [ARG...]

Run a command in a running container

Options:
  -d, --detach               Detached mode: run command in the background
      --detach-keys string   Override the key sequence for detaching a container
  -e, --env list             Set environment variables
      --env-file list        Read in a file of environment variables
  -i, --interactive          Keep STDIN open even if not attached
      --privileged           Give extended privileges to the command
  -t, --tty                  Allocate a pseudo-TTY
  -w, --workdir string       Working directory inside the container
  ...

⇒ "docker container ..." Commands

⇐ "docker" Commands vs. Management Commands

⇑ Docker Client (or CLI)

⇑⇑ Docker Container Platform - Tutorials