How to use the command `docker start` (with examples)

The docker start command is used to start one or more stopped containers. It allows you to resume the execution of containers that were previously stopped, enabling you to continue where you left off without losing any data or progress. This command is helpful when you want to restart a previously stopped container or run multiple containers simultaneously.

Use case 1: Show help

Code:

docker start

Motivation: Sometimes, when you’re unsure about the syntax or available options of a command, you may want to refer to the help documentation. This use case allows you to display the help information for the docker start command. It provides a quick and convenient way to access the command’s documentation.

Explanation: Running the docker start command without any arguments will display the help message, which includes a brief description of the command and a link to the official Docker documentation for more information.

Example output:

Start one or more stopped containers.

Usage: docker start [OPTIONS] CONTAINER [CONTAINER...]

Options:
  -a, --attach                  Attach STDOUT/STDERR and forward signals
  -i, --interactive             Attach container's STDIN
      --sig-proxy               Proxy all received signals to the process (default true)

Use case 2: Start a docker container

Code:

docker start container

Motivation: Starting a single container is a common use case when you want to resume the execution of a specific container that was previously stopped. This can be useful if you need to access data or services within that container or if you want to continue working on a specific project or task.

Explanation: In this use case, you should replace container with the actual name or ID of the container you want to start. By running this command, Docker will start the specified container, allowing you to resume its execution from the point where it was previously stopped.

Example output: No output is displayed if the container starts successfully. You can verify the status of the container by using the docker ps command.

Use case 3: Start a container, attaching stdout and stderr and forwarding signals

Code:

docker start --attach container

Motivation: Sometimes, you need to attach to the container’s stdout and stderr to view the output of the running container or to interact with its running processes. Additionally, forwarding signals can be helpful when you want to send signals (e.g., CTRL+C) to the container to gracefully terminate its execution.

Explanation: This use case demonstrates how to start a container and attach to its stdout and stderr streams by using the --attach option. By running this command, you will be able to see the output of the container in real-time. The --attach option also forwards signals to the container, allowing you to send signals to the running processes within the container.

Example output: The output will vary based on the specific container you start. You will see the container’s output directly in your terminal, providing real-time feedback of the container’s execution.

Use case 4: Start one or more space-separated containers

Code:

docker start container1 container2 ...

Motivation: You may have multiple containers that need to be started simultaneously. This use case allows you to start multiple stopped containers at once, saving you time and effort.

Explanation: By providing multiple container names or IDs separated by spaces, you can start multiple containers with a single command. This is useful when you want to start several related containers that depend on each other or need to work together.

Example output: No output is displayed if the containers start successfully. You can check the status of the containers using the docker ps command.