devops-shell-scripts A handbook for the bash that survives the first day on the job.

Act I · The Problem

The training script worked. The first job did not.

Most DevOps tutorials teach the happy path with unsafe defaults. The script runs once, the screen says "ok", the student learns the wrong habit. Then the same student lands at a real company, runs the same pattern against a real cluster, and an undefined variable expands to rm -rf / in front of the senior on call.

1. Pain · 01

   No set -e. No set -u. No pipefail.

   The script keeps running after a failed step. The exit code lies. The pipeline reports green. The pod is broken. The on-call learns the habit was never installed in the first place.

2. Pain · 02

   "It works on my machine" is the curriculum.

   The lab assumes the trainer's laptop. No container. No version pin. No idempotency. Re-running the script the second time blows up because the first run already created the resource. Real teams demand reruns.

3. Pain · 03

   Security is an afterthought, not a gate.

   SCA, SAST, secret scanning, container scanning, IaC policy, SBOMs. None of it is in the lab, none of it is in CI. The student ships a CV that says "DevOps" and walks into a DevSecOps interview unarmed.

4. Pain · 04

   The repo is one giant script, not ten small labs.

   You cannot study what you cannot isolate. A handbook needs a table of contents. Each lab needs to fail safely on its own. Each lab needs to lint, run, and clean up without taking the laptop with it.

Act II · The Promise

Safe defaults on line one. Every script. Every lab.

Bash has the discipline. Most curricula skip teaching it. This handbook puts the strict flags, the trap, the umask and the temp-dir cleanup at the top of every script. The student copies the pattern into the first job and never has to unlearn it.

#!/usr/bin/env bash
# ----------------------------------------------------------
# Safe-default lab script · Shoolini × L&T EduTech
# Run inside a container or throwaway VM, never on prod.
# ----------------------------------------------------------
set -Eeuo pipefail
shopt -s inherit_errexit nullglob
umask 077
IFS=$'\n\t'

readonly SCRIPT_NAME="${0##*/}"
readonly WORK_DIR="$(mktemp -d -t lab.XXXXXX)"

log()  { printf '[%s] %s\n' "$(date -u +%FT%TZ)" "$*"; }
die()  { log "FATAL: $*"; exit 1; }
need() { command -v "$1" >/dev/null || die "missing tool: $1"; }

cleanup() {
  local rc=$?
  rm -rf -- "$WORK_DIR"
  log "$SCRIPT_NAME exited rc=$rc"
  exit "$rc"
}
trap cleanup EXIT
trap 'die "interrupted"' INT TERM

# preflight · fail loudly, fail early
need docker; need kubectl; need shellcheck

# your lab here · idempotent, isolated, scoped to $WORK_DIR
log "workspace=$WORK_DIR"

Act III · The Curriculum

Ten labs. Each one ends with a habit the first job will reward.

Every lab lives in its own directory. Every lab is small enough to run on a 4 GB Linux VM or a Docker-in-Docker sandbox. Every lab finishes with a checklist the student walks into the office knowing.

Act IV · The Field Map

Twenty tools, two professions. Recognise them all on day one.

A junior engineer who can name and place these on a whiteboard is already an asset to the team. The handbook frames every lab against this map so the student leaves knowing where each tool sits in a real release.