Docker basic Command Line Tips and Tricks

In this tutorial, I will explain some important docker commands. I will explain some hands-on experience in how they are used and what they do.

Requirements

• A fresh server with Ubuntu 18.04 installed.
• A root password is set up on your server.

Update your System

First, it is recommended to update your system to the latest stable version. You can do it by running the following command:

Once your system is up-to-date, restart the system to apply the changes.

Install Docker

Next, you will need to install Docker CE on your server. By default, the latest version of Docker is not available in the Ubuntu 18.04 server default repository.

So, you will need to add the repository for that.

First, download and add Docker CE GPG key with the following command:

Next, add the Docker CE repository to APT with the following command:

Add the following line:

Save and close the file, when you are finished. Then, update the repository with the following command:

Once the repository is updated, install Docker CE with the following command:

After installing Docker CE, check the Docker service with the following command:

List Docker Commands

Let’s start with seeing all available commands docker have.

You can list all available docker command by running the following command:

You should see the following output:

To check system-wide information on docker, run:

You should see the following output:

To check docker version, run:

You should see the following output:

Downloading Docker Image

First of all, You will need to pull docker image because containers are built using docker image.

There are many images already available on docker website. You can found any image through a search.

For example to search Ubuntu 18.04 image, Run

You should see the following images available on docker website:

Next, Download the latest version of Ubuntu with the following command:

The output looks some thing like this:

Listing  Images

Once the download has been finished, You can list all available images on your system by running the following command:

The output looks some thing like this:

Running Docker Container

Now, to setup a basic ubuntu-18.04 container with a bash shell, you just run one command. docker run will run a command in a new container.

You’re now using a bash shell inside of a ubuntu docker container. To disconnect, or detach, from the shell without exiting use the escape sequence Ctrl-p + Ctrl-q.

Listing  Containers

By default, you can use the following command to list all running containers:

You can see the running container in the following output:

You can also list both  running and non-running containers by running the following command:

Sometimes container stops  due to its process ending or you stopping it explicitly. In this situation you can run container again with container ID.

Note: You can find container ID using docker ps command.

Stoping Container

To stop a container’s process, run:

Saving Container

If you would like to save the changes you have made with a container, use commit command to save it as an image.

For example, create new-ubuntu image from ubuntu with the following command:

Now, run the following command to see a newly created image:

You should see the following output:

This command turns your container to an image. You can roll back the container whenever you need.

Attach Docker Container

If we want to attach into a running container, Docker allows you to interact with running containers using the attach command.

You can use attach command with the container ID. The container id can be fetched using the command “docker ps”.

Inspect Docker Container

You can check every information about a Docker Container using the inspect command with container ID.

Stop and Delete all Containers

To stop all running containers, Run:

To delete all existing containers, Run:

To delete all existing images, Run:

Check Docker Log

If you run docker container as a daemon then it may be useful to know what appears on the console output of the running container. The docker logs command retrieves logs present at the time of execution.

You can use docker log command with container ID.

Conclusion

I hope you have now enough knowledge to work around with Docker command line. You can now easily start, stop, delete container and image using Docker cli. You can also did many stuff using Docker cli. For more information, you can refer Docker official doc at https://docs.docker.com/engine/reference/commandline/docker/