What is a (Docker) Container, really?

See slide #5 from a (shortened) K8s 101 which I always use to baseline and level-set the audience before diving into advanced container topics.

Transcript

1. 1
   Confidential ©2019 VMware, Inc.
   Kubernetes in a Nutshell
   

   View Slide

2. Confidential ©2019 VMware, Inc. 2
   „Kubernetes is an open-source System for
   automating Deployment, Scaling, and
   Management of containerized Applications.”
   The Origin of Kubernetes
   

   View Slide

3. Confidential ©2019 VMware, Inc. 3
   Google
   Search
   (late 1990s)
   Borg
   (~2003)
   Cgroups
   (2007)
   Omega
   (~2012)
   Docker
   (2013)
   The Origin of Kubernetes
   Kubernetes
   (2014)
   @embano1
   

   View Slide

4. Confidential ©2019 VMware, Inc. 4
   Kubernetes Cluster
   Kubernetes
   High-Level Architecture
   Infrastructure
   (Compute, Storage, Networking)
   Control Plane Worker
   Pod Pod Pod Pod Pod
   API
   Kubernetes
   Cloud Provider @embano1
   

   View Slide

5. Confidential ©2019 VMware, Inc. 5
   So what is a Container, really?
   Kernel Mode
   Cgroups
   Namespaces
   Security Capabilities
   Scheduler
   Syscall
   task_struct
   …
   Scheduling Entity (se)
   “running”
   syscall.Exec(ENTRYPOINT/CMD)*
   A Structure in Kernel
   Memory. The Kernel has
   no Notion of a
   “Container”. It’s yet
   another Executable.
   User Mode
   Docker Engine
   ContainerCreate()
   * After Container Sandbox Initialization
   (nsenter.go/nsexec.c)
   sched_class
   fair.c (CFS)
   @embano1
   

   View Slide

6. Confidential ©2019 VMware, Inc. 6
   The Pod – The atomic Unit in Kubernetes
   Kubernetes Primitives
   /pause
   Container #1 Container #2
   Pod
   Limits
   Requests
   https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.13/#podspec-v1-core
   Volumes
   Priority
   Affinity
   Probes
   IP
   @embano1
   

   View Slide

7. Confidential ©2019 VMware, Inc. 7
   Higher Level Objects
   Kubernetes Primitives
   Pod
   “redis--1”
   ReplicaSet “redis-”
   “desired: 3”
   Deployment “redis”
   “strategy: rollingUpdate”
   Pod
   “redis--2”
   Pod
   “redis--3”
   myCustomController
   “kind: redisCluster”
   Horizontal Pod Autoscaler
   (HPA)
   Metrics Provider
   myCustomController
   kubectl create –f redis.yaml
   REST API
   SDKs
   API
   

   View Slide

8. Confidential ©2019 VMware, Inc. 8
   Controllers and Reconciliation Loops
   Kubernetes Primitives
   Observe
   Analyze
   Act
   

   View Slide