Chapter 5. Pods

Question 1

What is a Pod ?

Answer 1

A Pod represents a collection of application containers and volumes running in the same execution environment. Pods, not containers, are the smallest deployable artifact in a Kubernetes cluster. This means all of the containers in a Pod always land on the same machine.

Question 2

What Do Pods share ?

Answer 2

1. Share the same IP
2. Share the same port space ( network namespace )
3. Have the same hostname ( UTS namespace )
4. can communicate using native interprocess communication channels over System V IPC or POSIX message queues (IPC namespace)

Applications in different Pods are isolated from each other

Question 3

What is the right question to ask yourself when designing Pods ?

Answer 3

Will these containers work correctly if they land on different machines?” If the answer is “no,” a Pod is the correct grouping for the containers. If the answer is “yes,” multiple Pods is probably the correct solution.

Question 4

What is a pod manifest ?

Answer 4

Pods are described in a Pod manifest. The Pod manifest is just a text-file representation of the Kubernetes API object. Kubernetes strongly believes in declarative configuration.

Question 5

Command to create a Pod:

Answer 5

kubectl run kuard –generator=run-pod/v1 \

–image=gcr.io/kuar-demo/kuard-amd64:blue

Question 6

Command to delete a Pod:

Answer 6

kubectl delete pods/kuard

Question 7

Command to access your pod:

Answer 7

kubectl port-forward kuard 8080:8080

Question 8

Command to access your log:

Answer 8

kubectl logs kuard

kubectl -f logs kuard

Question 9

Command to access your log from your previous instance of the container:

Answer 9

kubectl logs kuard –previous

Question 10

Command to get an interactive session:

Answer 10

kubectl exec -it kuard ash

Question 11

Command to execute command in the context of the container itself:

Answer 11

kubectl exec kuard date

Question 12

Copy files to and from Containers

Answer 12

kubectl cp :/captures/capture3.txt ./capture3.txt

Question 13

Copy files From and To Containers:

Answer 13

kubectl cp $HOME/config.txt :/config.txt

Question 14

What methods we can use to check application health ?

Answer 14

1. Liveness Probe
2. Readiness Probe
3. tcpSocket health checks
4. exec probes

Question 15

Which metrics Kubernetes allows to specify ?

Answer 15

1. Resource requests specify the minimum amount of a resource required to run the application.
2. Resource limits specify the maximum amount of a resource that an application can consume.

Question 16

How do you add volumes to a pod ?

Answer 16

By using:

1. spec.volumes: This array defines all of the volumes that may be accessed by containers in the Pod manifest
2. volumeMounts: This array defines the volumes that are mounted into a particular container, and the path where each volume should be mounted

Question 17

Name same ways of Using volumes with pods:

Answer 17

1. COMMUNICATION/SYNCHRONIZATION
2. CACHE
3. PERSISTENT DATA
4. MOUNTING THE HOST FILESYSTEM
5. Persisting Data Using Remote Disks