Tag: shellscript

set and unset in debug bash script

set-x = print actual shell command

set -f = disable filename expansion [ ls *.yml ]

errexit = fails all script if any exit code arrives

pipefail = Failes multi Pipe statement if any false statement 

set -x -f -o errexit -o pipefail
set +x +f +e

https://stackoverflow.com/questions/68465355/what-is-the-meaning-of-set-o-pipefail-in-bash-script

What Does Bash “set -x” do?

https://www.newline.co/courses/newline-guide-to-bash-scripting/errexit

https://unix.stackexchange.com/questions/333867/what-does-set-f-in-korn-shell-do

Custom Daemonset command based on host_ip in kubernetes

Why?
– When we need to add some extra functionally to daemonset based on which worker node it’s running on

apiVersion: apps/v1
kind: DaemonSet
metadata:
  labels:
    app: custom-daemonset
  name: custom-daemonset
spec:
  selector:
    matchLabels:
      app: custom-daemonset
  template:
    metadata:
      labels:
        app: custom-daemonset
    spec:
      containers:
      - command:
        - /bin/bash
        - -c
        - |
          echo "$STARTUP_SCRIPT" > /tmp/STARTUP_SCRIPT.sh
          /bin/bash /tmp/STARTUP_SCRIPT.sh
        env:
        - name: HOST_IP
          valueFrom:
            fieldRef:
              fieldPath: status.hostIP
        - name: STARTUP_SCRIPT
          value: |
            #!/bin/bash
            if [ $HOST_IP == "192.168.0.184" ]; then
              echo "HOST_IP is $HOST_IP"
            else
              echo "HOST_IP does not match $HOST_IP"
            fi
            sleep 600
        image: nginx
        imagePullPolicy: IfNotPresent
        name: custom-daemonset

Ref : https://github.com/kubernetes/kubernetes/issues/24657#issuecomment-577747926