Linux For Developers

A practical reference for developers working on Linux (Debian/Ubuntu-based).
Covers everyday commands, system internals, networking, package management, and more.

All examples are tested on Ubuntu/Debian. Most commands work on any Linux distro.

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Contents

Core Concepts

Topic	Description
Kernel	Kernel version, loaded modules, kernel messages
Linux Directory Structure	What every directory in / is for
Filesystem & Partitions	fdisk, partition schemes, GRUB
Environment Variables	env, export, printenv, setting vars
Path	How $PATH works, adding custom paths
Memory	free, /proc/meminfo
Swap	mkswap, swapon, swapoff

System Administration

Topic	Description
System Boot	initramfs, vmlinuz, init system
System Runlevels	Runlevel table (0–6)
Managing System Services	systemctl — start, stop, enable, disable
Process Monitoring	top, ps, uptime
Add New User	useradd, passwd, userdel
Upgrading & Patching	apt-get update, dist-upgrade, package ops
Using dpkg	List, inspect, and remove Debian packages

Networking

Topic	Description
Network & Interfaces	ip link, set IP, bring interface up/down, routing

Shell & Productivity

Topic	Description
echo & cat	Create and write files from the command line
Aliases	Define and manage shell shortcuts

Docker Internals

Topic	Description
Docker Internals	Image vs Container, OverlayFS, iptables, cgroups, namespaces
Kernel Deep Dive	Kernel vs OS, kernel space vs user space, syscalls

Utilities

Topic	Description
Video Editing (FFmpeg)	Trim, merge, combine audio/video, speed up
Check GPU Usage	Intel (intel_gpu_top) and Nvidia (nvidia-smi)
Convert PPTX to PDF	Batch convert slides with soffice

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Power User Commands

Estimate total video duration of all MP4s in a directory:

find . -iname '*.mp4' -exec ffprobe -v quiet -of csv=p=0 -show_entries format=duration {} \; \
  | paste -sd+ - | bc -l | awk '{printf "%.2f minutes\n", $1/60}'

Find which process is using a port:

sudo ss -tulnp | grep :8080

Watch real-time network traffic per interface:

watch -n 1 ip -s link

List all open files by a process:

lsof -p <PID>

Check disk usage, sorted by size:

du -h --max-depth=1 | sort -hr

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Quick Reference

# System info
uname -r              # kernel version
uname -a              # full system info
lsb_release -a        # distro info
uptime                # how long system has been running

# Disk
df -h                 # disk usage per filesystem
lsblk                 # block devices tree
sudo fdisk -l         # partition details

# Memory
free -mt              # RAM and swap summary
cat /proc/meminfo     # detailed memory info

# Processes
ps aux                # all running processes
top                   # live process monitor
kill -9 <PID>         # force kill a process

# Network
ip link               # all network interfaces
ip addr               # IP addresses
ping -c 4 google.com  # connectivity check
curl ifconfig.me      # your public IP

# Services
systemctl status <service>    # check service status
sudo systemctl restart nginx  # restart a service
journalctl -u nginx -f        # follow service logs