Linux and Shell Mastery Guide

Command fluency, scripting patterns, and troubleshooting checklists for cloud and Kubernetes hosts.

Linux and Shell Mastery Guide

Every container eventually runs on a Linux kernel. Platform engineers debug nodes, sidecars, and CI runners comfort on the shell is non-negotiable.

Command tiers

Tier 1 daily

Tier 2 weekly in production

Tier 3 incident mode

Research Core: Linux

Bash patterns worth memorizing

Copy
# Fail fast in scripts
set -euo pipefail
 
# Loop over files safely
while IFS= read -r -d '' file; do
  echo "$file"
done < <(find . -name '*.yaml' -print0)
 
# Retry with backoff
for i in 1 2 3 4 5; do
  curl -sf https://api.example/health && break
  sleep $((i * 2))
done

Troubleshooting playbooks

Disk full

1. df -h which mount?
2. du -sh /* largest top-level dirs
3. journalctl --disk-usage logs?
4. Rotate or truncate with approval; fix log shipping

High CPU

1. top which PID?
2. ps -p PID -o args what process?
3. Thread dump or profiler per application type
4. Scale horizontally if load is legitimate

Cannot SSH

1. Console access via cloud serial / rescue
2. Check sshd status, disk full, AllowUsers
3. Verify security group / NSG / firewall rules
4. Key permissions: chmod 600 private key

Security habits on servers

• No direct root SSH; use sudo with logging
• Unattended upgrades for security patches (with reboot window)
• CIS or vendor hardening baseline documented
• Auditd or equivalent for sensitive paths

Practice project

Build a bootstrap script that:

1. Creates a deploy user with sudo
2. Installs Docker or containerd
3. Configures fail2ban for SSH
4. Ships logs to a central collector (even a filebeat sidecar counts)

Commit to git with README portfolio-grade proof.