- June 1, 2017
- Posted by: Mahesh Kulkarni
- Category: Blogs
Docker – ‘A better way to build apps’, as stated on its website, is an open-source platform for building apps and microservices. The catch here is the automated deployment of your app in a container by OS–level virtualization provided by Dockers. Dockers are better than VMs as you can do away with the additional costs of maintaining and starting the latter. By deploying your app and its dependencies (i.e., the pre-requisite apps for its proper functioning) in a container, your app becomes portable during all the development and testing phases. Moreover, the isolated apps eliminate conflicts, enable team collaboration, and reduce the time-to-market.
When Do You Need to Use a Docker?
- For replicating the environment on your server, while running your code locally on your laptop
- For Docker CI/CD during numerous development phases (dev/test/QA)
- For distributing your app’s OS with a team, and as a version control system.
How Do You Setup a Docker Locally
- Download a Docker edition and the Docker Toolbox
- Make sure your BIOS has Virtualization Technologies, AMD-V, or KVM enabled
- Install the Extension Pack in the Oracle VirtualBox.
- Run the Setup
How Do You Use a Docker?
The most significant advantage of VMs is that they create snapshots that can be revisited instantly later. Docker containers enhance the lightweight process virtualization by being OS-independent and using the Linux Kernel’s functionality. They are made from Docker images – like snapshots. Docker images are created using a Docker file which can be customized or used as is. The default execution driver for creating a docker container is ‘libcontainer’. Docker Hub can be used to search docker images and see how they have been built.
- To create a Docker container, download the ‘hello world’ image by typing the following command in the terminal – $ docker run the hello world
- To check the number of images on your system, use the following command – $ docker images
- For searching an image in the Docker Hub – $ docker search <image>
Here’s a List of Docker Commands
- docker run: Executes command in a new container.
- docker ps: Lists running containers.
- docker ps -a: Lists all containers (including stopped ones).
- docker start: Starts stopped containers.
- docker stop: Halts running containers.
- docker restart: Restarts containers.
- docker login: Logs into a Docker registry.
- docker logout: Logs out from a Docker registry.
- docker rm: Removes a container.
- docker rmi: Removes an image.
- docker build: Creates an image from a Dockerfile.
- docker-compose: Manages multi-container Docker apps.
- docker version: Shows Docker version info.
- docker kill: Forces a container to stop.
- docker pull: Fetches an image from a registry.
- docker push: Sends an image to a registry.
- docker export: Saves a container’s filesystem as a tar.
- docker volume: Manages data volumes.
- docker exec: Runs a command in a running container.
- docker search: Looks for images on Docker Hub.
- docker images: Lists available images.
- docker attach: Connects to a running container.
- docker copy: Copies files/folders between container and host.
- docker commit: Creates an image from container changes.
- docker history: Shows image history.
- docker logs: Displays container logs.
- docker network: Manages Docker networks.
Let’s delve into key Docker commands and their applications. These fundamental Docker commands cater to both novices and seasoned practitioners.
1. docker run:
Docker initiates isolated processes within containers. A container is a self-contained unit running on a local or remote host. Upon executing ‘docker run’, the container process is independent, possessing its distinct file system, network, and process hierarchy separate from the host.
The fundamental ‘docker run’ command follows this structure:
Syntax Example: $ docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...]
Keynote:
- OPTIONS: Additional settings for the container, like ports mapping or resource constraints.
- IMAGE: The base image for the container.
- TAG|@DIGEST: (Optional) Specific version or hash of the image.
- COMMAND: (Optional) Initial command to run within the container.
- ARG…: (Optional) Arguments to pass to the command.
Understanding ‘docker run’ enables efficient container deployment and management.
2. docker start:
Resuming halted containers is achieved using ‘docker start’. This command revitalizes one or more previously paused containers, restoring their operational state.
Syntax example: $ docker start my_container
Keynote:
- my_container: Name or ID of the container to be restarted.
Employing ‘docker start’ facilitates the reactivation of paused containers, maintaining the workflow without losing prior configurations.
3. docker stop:
Terminates one or more active containers using ‘docker stop’. This command halts the execution of running containers gracefully.
Syntax Example: $ docker stop my_container
Keynote:
- my_container: Name or ID of the container to be stopped.
By invoking ‘docker stop’, you ensure proper closure of containers, allowing for a controlled exit and resource release.
4. docker build:
Creating images from Dockerfiles is facilitated by ‘docker build’. This command constructs an image based on instructions within a Dockerfile, streamlining image creation.
Syntax example: $ docker build [OPTIONS] PATH | URL
Key Points:
- OPTIONS: Additional settings for the build process.
- PATH | URL: Path to the Dockerfile directory or URL to a Git repository.
Leveraging ‘docker build’ enhances image management, enabling efficient customization and deployment.
Example: Build from a GitHub repository
$ docker build github.com/creack/docker-firefox
5. docker pull:
Fetching images or repositories from a registry and downloading them is achieved using ‘docker pull’. This command retrieves the specified image, making it available locally for usage.
Syntax example: $ docker pull [OPTIONS] NAME[:TAG|@DIGEST]
Key Points:
- OPTIONS: Additional settings for the pull operation.
- NAME: Name of the image or repository.
- TAG | @DIGEST: (Optional) Specific version or hash of the image.
Example: Pull an image named “dockerimage”
$ docker pull dockerimage
Utilizing ‘docker pull’ facilitates efficient image retrieval, ensuring seamless availability for local use.
6. docker export:
Converting a container’s filesystem into a tar archive is achieved through ‘docker export’. This command packages the container’s contents for external use or sharing.
Syntax examples:
$ docker export [OPTIONS] CONTAINER$ docker export red_panda > latest.tar$ docker export --output="latest.tar" red_panda
Key Points:
- OPTIONS: Additional settings for the export operation.
- CONTAINER: Name or ID of the container to be exported.
Using ‘docker export’ simplifies archiving container data for portability or distribution.
7. docker commit:
Generating a new image based on a container’s modifications is facilitated by docker commit. This command captures the altered container state as a reusable image.
Syntax example:
$ docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]$ docker commit c3f279d17e0a dev/testimage:version3
Key Points:
- OPTIONS: Additional settings for the commit operation.
- CONTAINER: Name or ID of the container to be committed.
- REPOSITORY[:TAG]: (Optional) Repository and tag for the new image.
Employing docker commit streamlines image creation from modified containers, promoting image versioning and customization.
If you want to know more, then check out the complete list of Docker commands here in the Docker documentation.
Step-by-Step Process of Using Docker on Windows
- You can run WordPress locally on your laptop by downloading Docker, without having to install Apache, PHP, MySQL etc. The Docker Toolbox creates a containerized version of Linux to run the Docker in a VM.
- Download Docker Tool Box which will install the Oracle VirtualBox.
- Install the Extension Pack in the VirtualBox.
- Type $ docker run hello-world in the terminal to check if your installation has finished correctly.
- Search for a WordPress image on the Docker Hub to install WordPress locally.
- Similarly, you can install DokuWiki using dockers.
- Dockers can be used for testing SDN components
Here are a few samples to get your docker engine up and running.
*All the examples in this article are for installing Docker commands on Windows. You can always run it on a Linux VM.
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What command should you run to see all running container in docker?
docker ps -a
you can use above command
docker ps
docker ps -a
docker ps
docker ps -a
docker container ls
docker ps -a
Docker ps (fetches all the running containers)
Docker ps -a (fetches all the running and stopped containers)
Docker ps -aq (fetches all the running containers with only containers ID)
You have to run the following command for seeing running container
docker ps
docker ps
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What command should you run to see all running container in docker?
Docker ps -here will list all running containers
docker ps -a here will list all running and stoped containers
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$ docker ps
it shows all the running dockers
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