App development and deployment now needs to be slicker and simpler than ever. To stay ahead of the competition, you need to be able to get your app up and running quickly without a ton of conflict issues or worrying that problems will arise depending upon which device is running it. That’s where the Docker container come into its own. But how do you create a Docker container? We look at some of the command lines you might use when manipulating your own Docker images and creating Docker containers.
Get in touch with Iron to find out more about how Docker and container frameworks can help your development get to the next level.
3 critical takeaways from the article:
- Docker is a platform for building, packaging, and distributing applications as lightweight containers.
- A Docker image is built from a Dockerfile using the "docker build" command.
- A Docker container is ran using the "docker run" command.
What is a Docker Container?
Docker containers allow tasks to be performed in isolation by running only the code and dependencies for that app/service and nothing else. Containers are the running instances of Docker images. So, in order to create a Docker container, first you have to source a Docker image. When you run that image and make it active, it becomes the container.
The architecture of Docker is that a user interacts with the client to manipulate Docker images. These are either created or pulled from an online source. Images are held on a Docker Host, and run as needed to become Docker containers.
Docker Hub is an online registry where the images you have created can be held. A Docker pull command will summon one (or more) of these images to the Docker host, where the image can be deployed as a container using the Docker run command. Users can log into Docker Hub and explore repositories to view available images.
Command line: docker pull <image name> or docker run <image name>
If you try to run an image which is not available on the local Docker host, the system should try to pull and run it directly from Docker Hub. You may see the following:
unable to find image ‘<image name>’ locally
…hopefully followed by a line advising the relevant image is being pulled from the library (Hub). Some images have tags for different versions which you can add into the command line using a colon directly after the image name.
To rename an image for your own use, use the following after your docker pull or docker run command:
--name <new name>
Creating the Container
Go to the command line of your system. Use the command docker create plus any relevant options. This command creates a layer over the original image which is writeable and ready to run specific commands. This allows full manipulation of Docker images without running them, although once the user is satisfied with their amendments the image can be run so that it becomes a container (see below).
How to Run or Stop a Docker Container
To run a container in interactive mode, use the following before the image name:
docker run -it <image name>
Using the command
allows you to see the details of the container which is running including status, original image name, and when it was created. The commands docker start <image name> and docker stop <image name> can be used to pause or un-pause a container.
docker stats <image name> allows a user to see how much memory the container is using.
Once a container is stopped, it will not accept any commands associated with running containers.
docker -a will show all the currently active containers. This is great if you need a reminder of the exact names of the Docker images you’re working with. Docker containers can then be removed with the command docker rm <image name>
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Benefits of Docker
Creating and using Docker containers is a major step up from virtual machines (VMs) because containers can work solely on the Cloud or via a virtual host. A traditional virtual machine requires a physical server to be split to emulate different run-time environments, meaning each VM has to carry an entire operating system as well as the code and dependencies of the app itself. Docker containers only carry the code and dependencies, meaning they use less space, are faster and more efficient.
Docker containers carry a Linux kernel with them so will work on any operating system without conflict - peace of mind in a world where apps need to work on a multitude of devices.
Related reading: Get to grips with the pros and cons of Docker.
IronWorker and Docker Containers
IronWorker is a container management tool specifically designed to work with the Cloud, supporting online work and helping app developers work faster and smarter. Set up background tasks, automation, and work how you want to work with a supportive tool that allows you to run a range of jobs from email to big data processing.
Related Reading: Serverless Architecture with Docker and IronWorker
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