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docker-architecture.md

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https://docs.google.com/presentation/d/1fC9cKR2-kFW5l-VEk0Z5_1vriYpROXOXM_5rhyVnBi4/edit#slide=id.gb6f3e2d2d_2_213

https://github.com/openshift-labs/learn-katacoda

ARCHITECTURE

  • Containers do not run ON docker. Containers are processes - they run on the Linux kernel. Containers are Linux.
  • The docker daemonis one of the many user space tools/libraries that talks to the kernel to set up container.

CONTAINERS ARE LINUX

Userspace libraries interact with the kernel to isolate processes

  • Libraries LXC, LXD, LibContainer, systemd nspawn, LibVirt
  • Kernel Data Structures NameSpaces, Cgroups, SELinux

THE USER SPACE TOOL CHAIN

On a Single Host

The user space tool chain adds the following:

  • A local daemon

  • Simple CLI/REST interface

  • Support for container images (OCI) and connection to registries

  • dockerd: This is the main docker daemon. It handles all docker API calls (docker run, docker build, docker images) through either the unix socket /var/run/docker.sock or it can be configured to handle requests over TCP. This is the 'main' daemmon and it is started by systemd with the /user/lib/systemd/system/docker.service unit file.

  • docker-containerd: Containerd was recently open sourced as a separate community project. The docker daemon talks to containerd when it needs to fire up a container. More and more plumbing is being added to containerd (such as storage).

  • docker-containerd-shim: this is a shim layer which starts the docker-runc-current command with the right options.

  • docker: This is the docker command which you typed on the command line.

THE ORCHECTRATION TOOLCHAINE

On Multiple Hosts

The orchestration toolchain adds the following:

  • More daemons ( it's a party) :)
  • Scheduling across multiple hosts
  • Application Orchestration
  • Distributed builds (OpenShift)
  • Registry (OpenShift)

CLASS ARCHITECTURE

Bringing it All Together

In distributed ssystems, the user must interact through APIs

THE COMMUNITY LANDSCAPE

Open Source, Leadership & Standards

The landscape is made up of committees, standards bodies, and open source projects:

  • Docker/Moby
  • Kubernetes/OpenShift
  • OCI (Open Container Intiative) Specifications
  • CNCF Cloud NAtive Copmputing Foundation Tecnical Leadership