Containerization

Question 1

What is a Container?

Answer 1

A lightweight, standalone, and executable software package that includes everything needed to run a piece of software

Question 2

What is an Image?

Answer 2

Container images are lightweight, standalone packages that include all the necessary elements for running software, such as code, dependencies, and system tools. They provide a portable and consistent environment, enabling applications to run reliably across various computing environments.

Question 3

What is a tag?

Answer 3

Attached at build time, used for versioning mostly

Question 4

What is “exposing a port” what things are needed?

Answer 4

Need to listen for traffic within the container
Need to forward traffic to a pod through the container

-p host-port:container-port

Question 5

What is a project?

Answer 5

Logical unit used to organize and isolate resources and applications within a container orchestration environment.

Question 6

What is a Pod?

Answer 6

A single instance of a running process. Shared network namespace, shared storage volumes.

oc create <spec>
oc delete pod <pod-name></pod-name></spec>

Question 7

What is a DeploymentConfig?

Answer 7

A template for a pod. An object that defines a desired state of a deployment and allows for declarative updates to applications

oc new-app <image> –name <name> –as-deployment-config
oc delete all -l <label></label></name></image>

Question 8

What is the ReplicaController? What does it work with?

Answer 8

When a new update is made to the deployment config, a new replication controller is made and the old one is deleted
Actually runs the pods

Question 9

What is a Service?

Answer 9

• Borrowed from Kubernetes
• Internal IP / DNA to expose a set of Pods
• Used for intercommunication between different components of an application within a cluster
• Load Balancing: automatically distribute incoming network traffic across the pods that match the service

oc expose –port <port> pods/<pod></pod></port>

Question 10

What is a Route?

Answer 10

Expose a service to the external open internet
Provides a publicly accessible URL

oc expose service/<service></service>

Question 11

What is a ConfigMap?

Answer 11

Borrowed from Kubernetes
Holds config data for pods to consume
“Consuming” configmap means using the data within the configmap
Not for sensitive data

oc set env dc/<deploymentConfig> -from cm/<configMap></configMap></deploymentConfig>

Question 12

What are secrets?

Answer 12

Openshift type
For private information

Question 13

What is an ImageStream?

Answer 13

Blueprint for a container
Correspond to names
Collection of related container images

Question 14

What is an ImageStreamTag?

Answer 14

Specific pointer or reference to a tagged image within an image stream
DeploymentConfigs can “subscribe” to an image stream tag
oc tag <original> <destination></destination></original>

Question 15

What are Builds?

Answer 15

Taking the source code of an application and creating an image from it

Question 16

What is a BuildConfig? What are Webhooks? What are Build Hooks?

Answer 16

oc new-build <source></source>

Webhooks
Endpoints triggered when devs push code, openshift starts build when called

Build Hooks
Do something after a build completes

Question 17

What is S2I?

Answer 17

Dockerfile not needed to produce an image
Create an image directly from source code using “builder images”

Question 18

What is HPA (Horizontal Pod Autoscaler)? What information is used?

Answer 18

Add replicas to a deployment config
oc scale dc/<deployment> –replicas=3</deployment>

Number of Pods
Current Resource Usage
Desired Resource Usage
oc autoscale dc/<deployment

config> –min 1 –max 1- –cpu-percent=80

Question 19

What are Templates?

Answer 19

Pre-configured set of openshift objects that can be used to create multiple instances of applications or services
Define and parameterize a group of resources
Includes services, routes, deployment configs, route, imageStream