devops-novice
devops-novice
Docker
Introduction
Containerization involves bundling an application together with all of its related configuration files, libraries and dependencies required for it to run in an efficient and bug-free way across different computing environments.
Docker is containerization technology which uses the Linux Kernel features to create containers on top of an operating system and automates application deployment on the container. Containers can be thought of as extremely lightweight, modular virtual machines. Docker is a platform to build, run, and share applications with containers.
Benefits of Docker
- Flexible: Even the most complex applications can be containerized.
- Lightweight: Containers leverage and share the host kernel, making them much more efficient in terms of system resources than virtual machines.
- Portable: You can build locally, deploy to the cloud, and run anywhere.
- Loosely coupled: Containers are highly self sufficient and encapsulated, allowing you to replace or upgrade one without disrupting others.
- Scalable: You can increase and automatically distribute container replicas across a datacenter.
- Secure: Containers apply aggressive constraints and isolations to processes without any configuration required on the part of the user.
Image vs Container
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Docker Image: An image includes everything needed to run an application - the code or binary, runtimes, dependencies, and any other filesystem objects required.
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Docker Container: A container is nothing but a running process, with some added encapsulation features applied to it in order to keep it isolated from the host and from other containers.
Docker Installation
Uninstall older Docker if any
sudo apt-get remove docker docker-engine docker.io containerd runc docker*
Set up the repository
Installing required packages
sudo apt-get update
sudo apt-get -y install
apt-transport-https
ca-certificates
curl
gnupg-agent
software-properties-common
Add Docker’s official GPG Key
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Verify key
sudo apt-key fingerprint 0EBFCD88
Setup stable repository
sudo add-apt-repository
"deb [arch=amd64] https://download.docker.com/linux/ubuntu
$(lsb_release -cs)
stable"
Install Docker Engine and docker-compose
sudo apt-get update
sudo apt-get install -y docker-ce docker-ce-cli containerd.io docker-compose
Add current user to docker group
sudo usermod -aG docker $USER
Log in and logout current user to avoid using docker commands with sudo
Start docker service
sudo systemctl enable docker
sudo systemctl start docker
Verify docker Installation
sudo docker run hello-world
Install Docker with a single script
Next: Docker Cheatsheet