Creating Objects Imperatively

Creating Objects Imperatively

This is intended to be a brief collection of commands. Read the other posts for more deets.
Kubectl docs cover imperative commands in extensive details.
Here, a mock use-case to setup a kuberenetes set of objects will be used as an example to illustrate a bunch of commands used to create & inspect k8s objects.

An Overview

Perhaps A use-case:
Another engineer has installed kubernetes and kubectl and has setup a node.
We are given several images to deploy and a handful of instructions:

deploy an api webserver from image web-sesrver:1.2.3 as a replicaset with a deployment object - use 3 instances of the image
deploy an nginx server as a "frontend" server with a deployment, replicaset, and 3 instances
deploy a db server from image mongodb:5.0.0, with a deployment, replicaset, and 1 instance
make them talk to each other: document and share some k8s object definition files to support these requirements
- the nginx (frontend) server will
  - accept requests from the world on port 80
  - make requests to the api server
  - should not be allowed to talk to or accept requests from anything else
- the api server will
  - accept requests from the frontend on port 1234
  - make requests to the db on port 27017
  - should not be allowed to talk to or accept requests from anything else
- the db server will
  - accept requests from the api server on port 27017
  - should not be allowed to talk to or accept requests from anything else
accept requests from the world using an ingress setup - the engineer already setup an nginx ingress controller && we need to config the ingress details to make ingress work

Terminal Ninja Commands

Using the bash cmd prompt can be cumbersome. Here are shome things to consider

Bash Aliases

Save Millions of Keystrokes.
Millions.

Consider using something like these to shortcut the ammount of times we need to wiggle our fingers.

Remember: 8 keystrokes saved, which is from kubectl get to kkg...

at 100x in a day is 800 keystrokes saved
over 5 days is 4,000 keystrokes
over 1 month, lets say 15 days at the previous rate, is 60,000 keystrokes
do this for 6 months and we save 360,000 keystrokes.

Write a few aliases to save a few keystrokes. save ourselves millions of finger-wiggles.

alias kk=kubectl
alias kkg"kubectl get"
alias kkd="kubectl describe"
alias kkc="kubeclt create"
alias kkdel="kubectl delete"
alias kkconf="kubectl config"

Imperative commands

Check out the kubectl cheatsheet docs for more.
Check out the generated reference docs also, for a different aspect on the imperative commands.


# show all current "api resource" types that are available
kubectl api-resources

# 
# CONFIG
# 
# see the config
kk config view
# context
kk config get-contexts
kk config current-context
kk config use-context some-named-context


#
# CONFIG: create config objects
#

# create a user in the kubeconfig file @ /root/.kube/config
#  LEVERAGE a client-cert from a file 
#  LEVERAGE a client-key from a file 
# kubectl config set-credentials <user-name> --client-certificate=/the/cert/file.crt --client-key=the/key/file.key
kubectl config set-credentials webappadmin --client-certificate=/webappadmin.crt --client-key=/webappadmin.key


# 
# Get info
# 
# get all
kk get (one of) | pods | deployments | netpol
kk get deployments
kk get netpol
kk get svc
# get a single
kk get pods pod-name
kk get netpol a-policy-name
kk get svc a-service-name

# WATCH the status of pods update
# note, this one needs ^C to cancel the terminal session
kk get pods --watch


# 
# Create a yaml before creating the resource
# -o yaml > the-file.yaml 
kk run api-pod --image=node:alpine --dry-run=client -o yaml > podfile.yaml



# 
# "Random"
# 
# all namespaces
kkg pods --all-namespace
# all namespaces shorthand
kkg pods -A

# get deployments AND pods, in oneline
kkg deployment,pod

# get more all at once
# replicasets, pods, services, endpoints
# for a list of ALL shortcuts and their types: https://kubernetes.io/docs/reference/kubectl/#resource-types
kkg deploy,rs,po,svc,ep

# 
# Taints
#

# un-taint a node
# note the "-" at the end removes the taint
mretfaster@cp:~$ kubectl taint nodes --all node-role.kubernetes.io/control-plane-
node/cp untainted


# 
# Process info
# 

# kk top: display resources by "type"
# https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#top
# show cpu + memory highlights
kk top nodes
kk top pods

Create Vs Apply

┌─────────┬───────────────────────┬────────────────────────┐
│ command │ object does not exist │ object already exists  │
├─────────┼───────────────────────┼────────────────────────┤
│ create  │ create new object     │          ERROR         │ 
│         │                       │                        │
│ apply   │ create new object     │ configure object       │
│         │ (needs complete spec) │ (accepts partial spec) │
│         │                       │                        │
│ replace │         ERROR         │ delete object          │
│         │                       │ create new object      │
└─────────┴───────────────────────┴────────────────────────┘

Copy Files Between Nodes

while the terminal is "in" a node, say the controlplane node, use the scp command (OpenSSH secure file copy) to copy to another node, say the node worker2:

controlplane$ scp path/to/files/on/host worker2:/path/on/worker2/node

Tags:

Kubernetes