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Kubernetes Basics or CKAD Theory Questions and Answers
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Kubernetes Basics or CKAD Theory
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Kubernetes Basics or CKAD Theorywhat is a pod - answer- abstraction of a server, minimal entity that can be managed by
k8s
- can contain multiple containers that has shared resources (volumes/ect) exposed by a
single IP address
- in real-work scenarios: pods are started through deployments
declarative vs imperative approach - answer imperative using the kubectl commands
(useful on exam)
declarative using yaml files (how it's done on real work for automation and checked-in
configs)
what is a sidecar container - answer- enhances or provides additional functionality to
the main container where it makes no sense on running on separate pod
- e.g logging, monitoring, synching
- the key is that the main container and the sidecar have access to shared resources to
pass info (e.g. volumes)
what is an ambassador container - answer- represents the primary container to the
outside world such as a proxy
- in java design pattern, think of front controller pattern
- in spring world, think dispatcherservlet
what is an adapter container - answeradopt the traffic or data pattern to match the traffic
or data pattern in other applications in the cluster
create namespace - answerkubectl create ns <name>
show all pods in all namespaces - answerkubectl get pods -A
or
kubectl get pods --all-namespaces
basic fields on all yaml resources - answerapiVersion, kind, metadata, spec
create a namespace in declarative way (generate yaml) - answerkubectl create ns
<namespace> --dry-run=client -o yaml
setup nano to be default k8s editor - answerexport KUBE_EDITOR=nano
edit file using nano with tab as 2 spaces - answernano <filename> -ET2
, split terminal window (so 1 is terminal, 1 for kubectl explain) - answertmux
ctrl+b to send command to tmux
list of commands after ctrl+b
% (to create a new vertical split)
" (to create a new vertical split)
o (to switch between splits)
x (to remove the split)
setup kubectl autocomplete and alias for kubectl -
answerhttps://kubernetes.io/docs/reference/kubectl/cheatsheet/ (bookmark this!)
env variables shortcut - answersudo -i (to eliminate any further issues later that might
required root)
alias kgc="kubectl config get-contexts"
alias ksc="kubectl config set-context --current --namespace"
export dr="--dry-run=client -o yaml"
export f="--force --grace-period=0"
inspect pods - answerkubectl describe <type> <name>
kubectl logs <pod name> -n <namespace> -c <container>
kubectl exec <pod name> -n <namespace> -c <container> -- <command here>
**or
kubectl exec -it <pod name> -n <namespace> -c <container> -- sh
port-forward - answerkubectl port-forward <pod> <localhostPort:containerPort>
defines privilege and access control settings for pod - answerSecurityContext
securitycontext how to use - answerpod.spec.securityContext
runAsNonRoot
runAsUser
fsGroup
pod for limited duration - answerjob (e.g. tasks like backup, calculation, batch
processing, etc)
job must have its restartPolicy to OnFailure or Never
- OnFailure will rerun the failing container on same pod
- Never will rerun failing container in a new pod
jobs spec - answerapiVersion: batch/v1
kind: Job
metadata:
name: test-job
spec:
completions: 3
parallelism: 1
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