Docker Easy: The Complete Guide on Docker World for Beginners by Charge Michael

Author:Charge, Michael [Charge, Michael]
Language: eng
Format: epub, pdf
Publisher: UNKNOWN
Published: 2020-09-08T16:00:00+00:00

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Chapter 3: Docker Commands & Architecture

3.1 Docker Commands

• Listing Containers

We have already seen, in this Docker tutorial, how to list the running containers using the ps command, but now what we want is to list all the containers, regardless of their state. Well, to do that, all we have to do is add the -a option as shown below:

docker ps -a

Now, we can easily distinguish between which container we want to start with and which one to remove.

• Removing Containers

After using a container, we would usually want to remove it rather than having it lying around to consume the disk space.

We can use the rm command to remove a container as shown below:

docker rm intellipaat-sql

• Removing Images

We already know how to list all the locally cached images using the images command. These cached images can occupy a significant amount of space, so in order to free up some space by removing unwanted images, we can use the rmi command as shown below:

docker rmi intellipaat-sql

Now, we know how to remove cached images, but what about the unwanted and unnamed images that we may end up generating during the debugging cycle of creating a new image? These images are denoted with the name, <none> . We can remove them all by using the following command:

docker rmi $(docker images -q -f dangling=true)

• Listing Ports

Knowing which ports are exposed by a container beforehand makes our work a lot easier and faster, e.g., Port 3306 is for accessing a MySQL database and Port 80 is for accessing a web server. Using the port command, as shown below, we can display all the exposed ports:

docker port intellipaat-sql

• Listing Processes

To display processing in a container, we can use the top command in Docker, which is much similar to the top command in Linux.

docker top intellipaat-sql

• Executing Commands

To execute commands in a running container, we can use the exec command.

For example, if we want to list the contents of the root of the hard drive, we can use the exec command as shown below:

docker exec intellipaat-sql ls /

We can gain access to the bash shell if we wish to ssh as root into the container we can use the following command:

docker exec -it my-est-mysql bash Note : All communications between Docker clients and Docker daemon are secure since they are already encrypted.

• Running Containers

The run command is one of the most complicated commands of all the Docker commands. Using this command, we can perform various tasks like configuring security and managing network settings and system resources such as memory, filesystems, and CPU. We can visit the following link to see and understand how to do all of the above and more using the run command.

3.2 Dockerfile

A Dockerfile contains all the instructions, e.g., the Linux commands to install and configure the software. Dockerfile creation, as we already know, is the primary way of generating a Docker image. When we use the build command to create an image, it can refer to a Dockerfile available on our path or to a URL such as the GitHub repository.

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