TOC.md

Introduction

Hello, and welcome to this tutorial!

During this journey you will, hopefully, get a better understanding of what Linux containers are and how they work.

We will achieve this by building a simple container engine together, incrementally, implementing new features as we introduce the necessary kernel primitives.

Containers: why?

• how we used to ship software:
  • copy-and-paste deployments
  • JARs
  • VMs?
  • ...
• the problems we had:
  • "runs on my machine"
  • lack of isolation
• containers as the solution

Containers do not exist

• containers are just an abstraction over some kernel primitives
  • this is not necessarily a bad thing!
• the building blocks of a Linux container
  • namespaces
  • cgroups
  • filesystems?

Running a process

• running a process
• returning the process exit code
• the UTS namespace

Getting our own root

• mount namespaces
• chroot vs pivot_root

Limiting our CPU usage

• the cpuset cgroup

Limiting our memory usage

• the memory cgroup

Making our filesystem changes ephemeral

• overlay filesystems
• using a loopback device?

What happens in Vegas stays in Vegas

• the PID namespace
• mounting the proc virtual filesystem to fix ps

Sharing folders with the host

• bind-mounts

Signaling containerised processes?

• pdeathsig?
• signal handling in Go?
• subreaper?

Devices

• mounting the dev virtual filesystem