DevOps is a natural evolution of software development. DevOps is not just a tool, a framework, or just automation. It is a combination of all these. DevOps aimed to align the Dev and Ops team with shared goals. A developer builds an application and sends it to the tester. But, the environments of development and testing systems are different; thus, the code does not work. There are two solutions to this: Docker and Virtual Machines.
Dockers have been used widely in many DevOps toolchains. Dockers platform provides numerous features that make it popular among developers. Some features include application isolation, portability, security management, Ease of software delivery, scalability, etc. Let's discuss the docker commands in more detail, along with examples! You can refer to the best Docker courses for training related to docker and docker commands.
Docker is a platform that enables the creation, deployment, and running of applications with the help of containers. A container is a unit of software that packages the code and all its dependencies together so that the application becomes runnable irrespective of the environment.
The container isolates the application and its dependencies into a self-contained unit that can run anywhere. Container removes the need for physical hardware, allowing for more efficient use of computing resources. Containers provide operating-system-level virtualization. Additionally, using Docker commands, developers can easily manage these containers, enhancing their productivity and workflow efficiency.
Let's understand a few of the above commands along with their usage in detail. The following are the most used docker basic commands for beginners and experienced docker professionals.
Here is the list of 50+ basic docker commands:
This command is used to get the current version of the docker
Syntax:
docker - -version [OPTIONS]
By default, this will render all version information in an easy-to-read layout.
Pull an image or a repository from a registry
Syntax:
docker pull [OPTIONS] NAME[: TAG|@DIGEST]
To download an image or set of images (i.e. A Repository) , Once can use docker pull command
Example:
$ docker pull dockerimage
This command is used to create a container from an image
Syntax:
docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
The docker run command creates a writeable container layer over the specified image and then starts it using the specified command.
The docker run command can be used with many variations, One can refer to the following documentation docker run.
This command is used to list all the containers
Syntax:
docker ps [OPTIONS]
The above command can be used with other options like - all or –a
docker ps -all: Lists all containers
Example:
$ docker ps
$ docker ps -a
This command is used to run a command in a running container
Syntax
docker exec [OPTIONS] CONTAINER COMMAND [ARG...]
Docker exec command runs a new command in a running container.
Refer to the following article for more detail regarding the usage of the docker exec command docker exec.
This command is used to stop one or more running containers.
Syntax:
docker stop [OPTIONS] CONTAINER [CONTAINER...]
The main process inside the container will receive SIGTERM, and after a grace period, SIGKILL. The first signal can be changed with the STOPSIGNAL instruction in the container’s Dockerfile, or the --stop-signal option to docker run.
Example:
$ docker stop my_container
This command is used to restart one or more containers.
Syntax: docker restart [OPTIONS] CONTAINER [CONTAINER...]
Example:
$ docker restart my_container
This command is used to kill one or more containers.
Syntax: docker kill [OPTIONS] CONTAINER [CONTAINER...]
Example:
$ docker kill my_container
This command is used to create a new image from the container image.
Syntax: docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
Docker commit command allows users to take an existing running container and save its current state as an image
There are certain steps to be followed before running the command
Example:
$ docker commit c3f279d17e0a dev/testimage:version3.
This docker command is used to push an image or repository to a registry.
Syntax: docker push [OPTIONS] NAME[: TAG]
Use docker image push to share your images to the Docker Hub registry or to a self-hosted one.
Example:
$ docker image push registry-host:5000/myadmin/rhel-httpd:lates
Apart from the above commands, we have other commands for which the detailing can be found in the following link Docker reference.
This command is used to remove one or more docker containers. We can use options such as -f i.e. force removal of running container which internally uses SIGKILL. Or -v which removes any anonymous volumes associated with the container.
Syntax: docker rm [OPTIONS] CONTAINER [CONTAINER...]
Example:
docker rm container1
Removing multiple containers:
docker rm container1 container2 container3
Removing with -v and -f options:
docker rm -v container1
docker rm -f running_container
This command is used to remove one or more docker images from the system. We can use some common options such as - f for force removal of an image or --no-prune for not deleting untagged parent images.
Syntax:
docker rmi [OPTIONS] IMAGE
Remove a single image:
docker rmi my_image:tag
Remove multiple images:
docker rmi image1:tag image2:tag image3:tag
Force remove an image:
docker rmi -f my_image:tag
Removing image without deleting untagged images:
docker rmi --no-prune my_image:tag
This command is used to upload the docker image to a Docker registry such as Docker Hub or a private registry.
Syntax: docker push [OPTIONS] NAME[:TAG]
Example:
Command: docker push myusername/myrepository:latest
This command is used to log in to the Docker registry such as Docker Hub, a private registry, or any other third-party registry. We can use some common options such as -u for the username of the registry, -p for the password of the registry.
Syntax: docker login [OPTIONS] [SERVER]
Examples:
Login to Docker Hub: docker login
Command: docker login
Login with username and password:
Command: docker login -u myusername -p mypassword
Note: In case we need to log in to other Docker registries:
Command: docker login myregistry.com
This command is used to start one or more containers. We can use common options such as -a to attach stderr /stdout and forward signal. Also -i option can be used as an interactive mode where the container STDIN can be attached.
Syntax: docker start [OPTIONS] CONTAINER [CONTAINER...]
Example:
Starting Single Container:
Command: docker start container1One can become DevOps certified by referring to DevOps Certification courses.
Here are the top 57 essential/ basic docker commands with descriptions to learn and use.
| Command | Usage |
|---|---|
| docker attach | Attach local standard input, output, and error streams to a running container |
| docker build | Build an image from a Dockerfile |
| docker builder | Manage builds |
| docker checkpoint | Manage checkpoints |
| docker commit | Create a new image from a container’s changes |
| docker config | Manage Docker configs |
| docker container | Manage containers |
| docker context | Manage contexts |
| docker cp | Copy files/folders between a container and the local filesystem |
| docker create | Create a new container |
| docker diff | Inspect changes to files or directories on a container’s filesystem |
| docker events | Get real time events from the server |
| docker exec | Run a command in a running container |
| docker export | Export a container’s filesystem as a tar archive |
| docker history | Show the history of an image |
| docker image | Manage images |
| docker images | List images |
| docker import | Import the contents from a tarball to create a filesystem image |
| docker info | Display system-wide information |
| docker inspect | Return low-level information on Docker objects |
| docker kill | Kill one or more running containers |
| docker load | Load an image from a tar archive or STDIN |
| docker login | Log in to a Docker registry |
| docker logout | Log out from a Docker registry |
| docker logs | Fetch the logs of a container |
| docker manifest | Manage Docker image manifests and manifest lists |
| docker network | Manage networks |
| docker node | Manage Swarm nodes |
| docker pause | Pause all processes within one or more containers |
| docker plugin | Manage plugins |
| docker port | List port mappings or a specific mapping for the container |
| docker ps | List containers |
| docker pull | Pull an image or a repository from a registry |
| docker push | Push an image or a repository to a registry |
| docker rename | Rename a container |
| docker restart | Restart one or more containers |
| docker rm | Remove one or more containers |
| docker rmi | Remove one or more images |
| docker run | Run a command in a new container |
| docker save | Save one or more images to a tar archive (streamed to STDOUT by default) |
| docker search | Search the Docker Hub for images |
| docker secret | Manage Docker secrets |
| docker service | Manage services |
| docker stack | Manage Docker stacks |
| docker start | Start one or more stopped containers |
| docker stats | Display a live stream of container(s) resource usage statistics |
| docker stop | Stop one or more running containers |
| docker swarm | Manage Swarm |
| docker system | Manage Docker |
| docker tag | Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE |
| docker top | Display the running processes of a container |
| docker trust | Manage trust on Docker images |
| docker unpause | Unpause all processes within one or more containers |
| docker update | Update configuration of one or more containers |
| docker version | Show the Docker version information |
| docker volume | Manage volumes |
| docker wait | Block until one or more containers stop, then print their exit codes |
Let's understand a few of the docker use cases:
Use case 1: Developers write their code locally and can share it using docker containers.
Use case 2: Fixing the bugs and deploying them into the respective environments is as simple as pushing the image to the respective environment.
Use case 3: Using docker one can push their application to the test environment and execute automated and manual tests
Use case 4: One can make their deployment responsive and scalable by using docker since docker can handle dynamic workloads feasibility.
When a company wants to develop a web application, it needs an environment where they have a Tomcat server installed. Once the tester set up a tomcat environment and test the application, it is deployed into a production environment. Once again the tomcat has to be setup in a production environment to host the java web application There are some issues with this approach:
Now, let's see how the Docker container can be used to prevent this loss.
In order to overcome the issues, docker will be used by a developer to create a docker image using a base image which is already existing in Docker hub. Docker hub has some base images available for free. Now this image can be used by the developer, tester, and the system admin to deploy a Tomcat environment using Docker Commands. In this way, Docker container solves the problem.
Docker architecture generally consists of a Docker Engine which is a client-server application with three major components:
DevOps (development + operations) is an evolution born between developers and system administrators. One of the main tasks of DevOps is the automation and centralization of software development and deployment. One of the most popular tools that helps solve this task is Docker. To get a better understanding of Docker commands and more, enroll in Docker Kubernetes training.
Three main features of Docker products are the most distinguishing:
Learning the top Docker commands is essential for any DevOps professional looking to streamline container management and deployment processes. As you continue to explore and learn more about Docker, keeping these commands at your fingertips will prove invaluable in your journey toward DevOps operational excellence.
Docker CLI (command line interface) is a command-line tool that is used to interact with the docker daemon. To get the list of commands either run docker with no parameters or execute the docker help command.
Docker has 13 Management commands and 41 general commands. One can run the docker command using the docker CLI tool. To list available commands, either run docker with no parameters or execute docker help.
An image is a read-only template with instructions for creating a Docker container. The container is a runnable instance, while image is a read only template of it. Using the command docker pull one can get the images from the docker registry.
One can run a docker command using the Docker CLI tool. Docker command line interface tool is preferably used to run docker commands Docker CLI tool can be installed along with docker.
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