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, but Docker is far better in terms of performance, scaling, and efficiency.
Docker is a platform that has eased application development for both developers and system managers. Dockers have been used widely in many DevOps toolchains. Docker provides flexibility for the operational team thereby reducing the risk overhead. Dockers platform provides numerous features which make them popular among developers. Some features include application isolation, portable, security management, Ease of software delivery, scalability, etc. Let's discuss the basic docker commands in more detail along with examples! You can refer to the best Docker courses for training related to docker and docker commands.
What is Docker?
Docker is a platform that enables creating, deploying, and running applications with the help of containers. A Container is a unit of software that packages the code and all its dependencies together such 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. Moreover, developers can collaborate faster without worrying about which software dependency they need to install.
A container is a runnable instance of an image. An image is a read-only template with instructions for creating a Docker container. You can create, start, stop, move, or delete a container using the Docker API or CLI. One can connect a single container to one or more networks and can also attach storage to it. A new image can also be created based on the current state of the container. Containers can be shared thereby ensuring that everyone who communicates with it will get the same container and that works in the same way. Here is the list of 50+ basic docker commands:
List of 57 Essential Docker Commands
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 above commands along with their usage in detail. The following are the most used docker basic commands for beginners and experienced docker professionals.
1. docker –version
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.
2. docker pull
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 3. docker run
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.
4. docker ps
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
5. docker exec
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.
6. docker stop
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
7. docker restart
This command is used to restart one or more containers.
Syntax: docker restart [OPTIONS] CONTAINER [CONTAINER...]
Example:
$ docker restart my_container
8. docker kill
This command is used to kill one or more containers.
Syntax: docker kill [OPTIONS] CONTAINER [CONTAINER...]
Example:
$ docker kill my_container
9. docker commit
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
- First , Pull the image from docker hub
- Deploy the container using the image id from first step
- Modify the container (Any changes ,if needed)
- Commit the changes
Example:
$ docker commit c3f279d17e0a dev/testimage:version3.
10. docker push
This 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.
One can become DevOps certified by referring to DevOps Certification courses.
Docker Use Cases
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.
Let us take an example of an application,
When a company wants to develop a web application they need 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 production environment to host the java web application There are some issues with this approach:
- Loss of time and effort.
- Developer and tester might use a different tomcat versions.
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 developer, tester and the system admin to deploy a tomcat environment. In this way, Docker container solves the problem.
Docker Architecture
Docker architecture generally consists of a Docker Engine which is a client-server application with three major components:
- Generally, docker follows a client-server architecture
- The client communicates with the daemon, which generally takes up the task of building,running, and shipping the docker containers.
- The client and daemon communicate using REST API calls. These calls act as an interface between the client and daemon
- A command-line interface, Docker CLI runs docker commands. Some basic docker commands with examples are listed in the next section.
- Registry stores the docker images
Conclusion
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 help in solving this task is Docker. To get a better understanding of docker enroll in Docker Kubernetes training.
Three main features of Docker products are the most distinguishing:
- Quick deployment in a variety of environments
- Greatly facilitated testing
- Possibility of using Docker as a development environment.
