This document provides an overview of Kubernetes concepts including: - Docker containers are individual processes that make up applications, not complete applications themselves. - Kubernetes manages container deployments through services that define relationships between containers and provide load balancing, discovery, scaling, updates and rollbacks. - Kubernetes was created by Google and is supported on platforms like Google Kubernetes Engine, Azure Container Service, and others. - Kubernetes manages clusters of nodes that host containers through masters nodes that control workers. - The basic building block is the Pod, which contains one or more containers that share resources and networking.

1. Hesham Amin
http://heshamamin.com/
@heshamamin
https://www.linkedin.com/in/heshamaamin/

2.  Docker container = Process
 Not a complete application (Usually)
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3.  Coordinate containers deployment
 Define relations between containers
 Load Balancing
 Service discovery
 Scale
 Rolling updates
 Rollback
 Management
 Resource optimization
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4.  By Google
 Supported on GKE
 Azure Container Service
 Others (AWS / On-prem)
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6. Node
Master(s)
Kubelet
API
Proxy
Node
Node
Kubelet
Azure load
balancer
Availability set

7.  Collections of nodes and other resources
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8.  Virtual or Physical machines
 Worker Node is a machine that hosts the containers
 Master nodes: control workers
 Created by the host and registered with Kubernetes
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9.  The smallest logical unit of deployment
 Collection of containers
 Usually one
 Share IP and port space (localhost)
 Not durable
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apiVersion: v1
kind: Pod
metadata:
name: pod-example
labels:
env: test
spec:
containers:
- image: nginx
name: nginx

11.  Abstraction which defines a logical set of Pods and a policy by which to access
them.
 This set of Pods are determined using selectors.
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kind: Service
apiVersion: v1
metadata:
# Unique key of the Service instance
name: service-example
spec:
ports:
# Accept traffic sent to port 80
- name: http
port: 80
targetPort: 80
selector:
# Loadbalance traffic across Pods matching
# this label selector
app: nginx
# Create an HA proxy in the cloud provider
# with an External IP address - *Only supported
# by some cloud providers*
type: LoadBalancer

13.  Declarative desired state of Replica Sets
 Support scaling and autoscaling
 Can be rolled-back
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apiVersion: extensions/v1beta1
kind: Deployment
metadata:
# Unique key of the Deployment instance
name: deployment-example
spec:
# 3 Pods should exist at all times.
replicas: 3
# Keep record of 2 revisions for rollback
revisionHistoryLimit: 2
template:
metadata:
labels:
# Apply this label to pods and default
# the Deployment label selector to this value
app: nginx
spec:
containers:
-name: nginx
# Run this image
image: nginx:1.10

15.  Ensure a specified number of Pods is running at any time
 Used for scaling
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16.  Group of Stateful Pods.
 Stable, unique network identifiers.
 Stable, persistent storage.
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17.  Scope for names. Names of resources are unique within a namespace.
 A way for managing resource quotas:
 Number of objects
 Memory
 CPU Cores
 Used for large clusters.
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