Table of content: https://docs.google.com/document/d/1IIOkivkS0lV9QIL16b_OjT480BxZHQfKswvvS-CVZlw/view

Docker

Setting up

https://docs.docker.com/install/linux/docker-ce/debian/

1. Trust Docker's key
2. Add repository
3. Update
4. Install package
5. Test: "docker --version", "sudo docker run --rm -it hello-world"
6. Add rights to user

Typical Docker command

# docker run --rm -it alpine /bin/sh

Unable to find image 'alpine:latest' locally

latest: Pulling from library/alpine

b56ae66c2937: Pull complete (Downloading, Extracting)

Digest: sha256:d6bfc3baf615dc9618209a8d607ba2a8103d9c8a405b3bd8741d88b4bef36478 Status: Downloaded newer image for alpine:latest

/ # echo hello

hello

Dockerfiles

Simple sample Docker file:

FROM alpine:latest

RUN \

    echo hello > /world.txt

COPY myshell /theshell

ENTRYPOINT /theshell

Command line:

docker build . -t mycontainer

docker run --rm -it mycontainer

"Pillars" of Docker

• Isolation: namespaces and cgroups
• Layered filesystem

• Reproducible builds

• Network infrastructure

• Share pre-built images

Isolation levels

• No isolation
• User accounts
• User-space containers (LXC, Docker on Linux)

• Isolated network (can be opted out)
• Isolated filesystem (but can share mounts)
• Processes grouped together
• Resources usage
• Still same Linux kernel

• Virtual machine (also Docker on non-Linux)

• Isolated network (unavoidable)
• Isolated block device (tricky to share files)
• Separate Linux kernel

• Physical machine

• Most secure
• Most performant (but can be close to virtual machine)

Cloud approach vs classical approach

Classical approach

• "Pet" servers

• Gateway
• Database server
• Web server
• Logging server

• Physical machine -> OS -> App
• Can't easily rearrange and manage resources

Cloud approach

• "Cattle" servers

• node1
• node2
• node3

• Most servers are the same: Physical machine -> OS -> Virtualization solution
• Virtual machine (or Docker) -> App
• Can move applications between servers
• Can add more servers easily