Get started with docker

Docker concepts:
Docker is a platform for developers and sysadmins to develop, deploy, and run applications with containers

Containerization's advantages:

• Flexible: Even the most complex applications can be containerized
• Lightweight: Containers leverage and share the host kernel
• Interchangeable: You can deploy updates and upgrades on-the-fly
• Portable: You can build locally, deploy to the cloud, and run anywhere
• Scalable: You can increase and automatically distribute container replicas
• Stackable: You can stack services vertically and on-the-fly

Images and containers

• A container is launched by running an image. An image is an executable package that includes everything needed to run an application--the code, a runtime, libraries, environment variables, and configuration files.

• A container is a runtime instance of an image--what the image becomes in memory when executed (that is, an image with state, or a user process). You can see a list of your running containers with the command, docker ps, just as you would in Linux.

Containers and virtual machines

• A container runs natively on Linux and shares the kernel of the host machine with other containers. It runs a discrete process, taking no more memory than any other executable, making it lightweight.

• By contrast, a virtual machine (VM) runs a full-blown “guest” operating system with virtual access to host resources through a hypervisor. In general, VMs provide an environment with more resources than most applications need.

1. list the images that was downloaded to your machine

docker image ls

2. list containers which exits after displaying its message. If it were still running, you would not need to use --all option

docker container list --all