CoreOS, Docker, Kubernetes Notes

Notes on CoreOS

build of ChromeOS
very lightweight, no extra pieces
not even a package manager
all apps are expected as docker containers
on boot:
loads "clound-config"
loads etcd (daemon)
highly-available/globally distributed key-value store
each node runs its own ectd client
passes configuration between nodes
used for service-discovery (e.g. a load balancer queries etcd for ip address of backend services)
to get the data: http://127.0.0.1:4001/v2/keys/ or utility etcdctl
loads "fleet" (daemon) to schedule, manage apps across cluster
fleet is a system wide init
fleet ties into nodes systemd
constraining the deployment targets
start or stop services on less busy nodes!
specify conditions for starting service
fleetctl
- schedule services
- manage nodes
- general state of systems

Docker

containerization system utilizes LXC
uses kernel namespacing and cgroups to isolate processes
act as individual servers running side by side over each other
vs virtualization: doesn't emulate OS only implements whats necessary to run app

Kubernetes - pronounced koo-ber-nay'-tace

manage containerized apps across a cluster of nodes
unit of work is a service, can have member nodes, user shouldn't care where work is done.
Controlling unit called "master" service
directs communications across system
uses etcd, but is more fleiible than CoreOS implementation
runs API server
etcd store and service details of containers are in agreement
kubecfg and RESTful interface
manager service watches for changes on etcd acts accordingly Kubernetes minions - where the work is done
communicate with master
network containers
docker service is required
dedicated subnet for each minion is available so ports can be exposed correctly Kubelet -
service communicates with master server to receive commands and work
work is received as a manifest Pod
closely related containers grouped on pd
involved containers scheduled on hosts
share volumes and ip space

pricees/coreos_docker_kubernetes_notes.md