What is Docker?
Docker is one of the coolest technologies we have today which allows you to run small and independent services on a single bit of hardware called ‘Containers’(small versions of virtual machines). Docker is a tool that permits developers, sys-admins, and others to easily deploy their applications in these Containers that run on the host operating system Linux.
Basically Docker is very beneficial since it permits users to package an application with all of its dependencies into one standardized unit for software development. Contrasting to virtual machines, containers borrow some features from their OS and so are extremely lightweight, more flexible and more efficient as they do not bear a high overhead.
Learn how to use Docker with a super-easy tutorial and get all the knowledge you need about containers.
What are Containers?
To know how to use Docker, we should first understand what is a Container?
A container is a lightweight virtual machine which runs on the same OS kernel on the same piece of hardware.
In the case of a “traditional” virtual machine, which has its own operating system; you have to assign Virtual CPU cores to that VM. Though it is great for having full isolation, it drains your resources quickly.
Benefits of Containers:
- It saves a lot of resources so that you can have even containers with 50MB of RAM.
- Each container enables you to run micro-services. Thus you can have several containers, each with a simple and specific role.
- To have several web servers you need to reserve CPU power and RAM space for the operating system. Containers resolve this problem by enclosing all the containers to share the same OS Kernel, one of the Docker engines.
How to use Docker?
Docker is the software which runs and controls containers. Use these 7 simple steps,and let’s get started.
Step 1- Installing Docker
Installing Docker is obviously the first thing we need to do. Fortunately, it’s quite simple on both Windows and Linux.
On Windows, you have a wizard that shall do almost everything for you. You can simply visit the official download page for Windows and Mac.
And On Linux you have to use a package manager.
After you finish with the installation, you get the Docker command in the prompt or terminal.
Step 2- Docker Pull
After you have the docker software installed, the next step is to get a docker image. You can install docker containers from docker images, if you install the machine OS from a DVD or the OS of a VM from ISO file. However, to get these docker images first, you need to use the docker pull command.
Docker automatically connects to the docker hub servers and searches for public images that are available to the public. You can also organize your docker to pull images from a private repository too.
Step 3- Docker run
Now we are ready to use docker. The docker run command lets you run containers based on images. It is like running a virtual machine with a précised OS, simply with containers. Instead of selecting the OS, here you need to select the image.
You can basically run docker run followed by the image name. Don’t forget to name your container with the –name option. Another selection you need to use is –d. On running a container as detached (-d), will print the container ID in the background.
Step 4- Listing containers
Now you need to check the list of containers, with docker container ls option.
This will display only the active running containers. Also if you want to see all the containers you have, including the ones which are not running currently, you can use docker container ls -a.
Step 5- Managing the docker containers
If you want to use docker, you must also know how to manage your docker containers. Since your container is like a virtual machine, you typically don’t need to destroy it unless it’s run out. Instead, just shut it down and turn it back on at regular intervals when required. Do it the help of two commands; docker stop and docker start both followed by the container name or ID:
One more important command is exec, which will allow you to run commands inside the container like you can run CLI commands inside of a virtual machine.
Step 6- Storage persistence
The final part of knowing how to use docker is all about storage. Each container stores its information in a volume by default. Whenever you create a container using docker run , docker automatically creates a volume, which gets destroyed when the container is destroyed. But you may need the volume to continue existing for any future requirement like if you want to attach that volume to another container.
In such a case, first create the required volume with docker volume create, followed by the volume name. Additionally you can also list all your volumes with use of docker volume ls. Then, when you run a container, to specify the use of a pre-created volume, use -v, followed by the volume name.
Images come with their default docker file that allows you to create your own, custom, container and you can use it to tailor the containers as per your needs.
So now you know how to use Docker to create and manage containers from existing images. Hopefully now you can run your small container-based data center even on your laptop to create better applications.
What is your opinion now about docker?
Would you like to see yourself using it more often?
With this how to use Docker you are now well equipped with all the Docker knowledge, and so fully ready to get to deploying web applications with Docker!
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