Linux Survival Basics
The commands to inspect a machine before guessing.
linux fixes you can inspect first
Fix the Linux problem in front of you.
Short, copyable commands for common Linux, hosting, server, and terminal problems. Every published fix includes safety notes, when not to use it, and simulated output from a disposable demo environment.
Current library
285 checked one-liners across Linux basics, web hosting, dangerous commands, and server triage.
285/285 commands have disposable demo output.
problem areas
Browse by what broke
Web Server Rescue
Small checks that separate DNS, TLS, Nginx, and app failures.
Dangerous Commands
Commands worth understanding before copying from the internet.
Cybersecurity Triage
Defensive commands for checking exposure, logs, permissions, and suspicious activity.
Hosting Operations
Web hosting, SSL, DNS, Nginx, deployment, backups, and VPS management.
Apple Terminal
macOS and Apple-adjacent terminal workflows for developers and power users.
verified fixes
Start here
A focused entry set from the 285-lesson library. Use the problem areas for the full catalog.
Your Site Is Not Down. DNS Might Be Lying.
The browser said the site was gone. The server was answering fine.
curl --resolve example.com:443:203.0.113.10 https://example.com/
Find the Files Eating Your Disk
The disk was full, but guessing at folders was the slow part.
find /var -type f -printf '%s %p\n' | sort -nr | head -20
Run Rsync Without Deleting Your Backup
One rsync flag can save you. Another can erase the wrong side.
rsync -avhn --delete ./source/ ./backup/
Watch Logs Without Opening the Whole File
The app was failing now. Opening a giant log file was the wrong move.
tail -n 80 -f /var/log/nginx/error.log
Find Errors Before Reading Every Log Line
The error was in the log. The problem was finding it without reading noise.
grep -iE 'error|failed|denied|timeout' /var/log/nginx/error.log | tail -40
Check What Is Actually Listening
The app was running. The port was not listening.
ss -tulpn | grep ':80\|:443'
Inspect Permissions Before Changing Them
The permission fix was easy. Knowing what not to chmod was the hard part.
namei -l /var/www/example/index.html
Find the Exact Log Line Before You Scroll
The error was there. The useful part was knowing exactly where it was.
grep -inE 'error|failed|denied|timeout' /var/log/nginx/error.log
Find Which Folder Is Filling the Disk
The disk was full. The fastest clue was the folder, not the file.
du -sh /var/* 2>/dev/null | sort -h
Show Only Recent Errors
The log had old failures too. I only cared about the newest ones.
grep -iE 'error|failed|denied|timeout' /var/log/nginx/error.log | tail -10
Preview What Rsync Would Delete
`rsync --delete` is useful. It is also how people erase the wrong side.
rsync -avhn --delete ./source/ ./backup/ | grep '^deleting'
Check Owner and Mode in One Line
The file existed. The owner and mode explained why it still failed.
stat -c '%A %U:%G %n' /var/www/example/index.html
Find the Processes Using Memory
The server felt slow. Memory pressure was the first thing to rule out.
ps -eo pid,comm,%mem,%cpu --sort=-%mem | head
Show Big Files in Human Units
Byte counts are precise. Human units are faster under pressure.
find /var -type f -printf '%s %p\n' | sort -nr | head -10 | awk '{printf "%.1f MB %s\n", $1/1024/1024, $2}'
Find What Is Using a Local Dev Port
Your dev server says port 3000 is busy. Ask macOS who is holding it.
lsof -nP -iTCP:3000 -sTCP:LISTEN
Stop the Process Blocking a Dev Port
Free a stuck dev port without hunting through Activity Monitor.
lsof -ti tcp:3000 | xargs kill
Show Your PATH One Entry Per Line
Wrong Node, Python, or FFmpeg? Start by reading your PATH clearly.
echo "$PATH" | tr ':' '\n' | nl -ba
See Exactly Which Command macOS Will Run
Before blaming npm, Python, or Git, check the binary your shell actually found.
command -v node && node -v
Find Large Files Inside a Project
Before committing, check whether a huge video, build artifact, or export slipped into your repo.
find . -type f -size +100M -print
Find Which Folder Is Eating Disk Space
When your Mac is full, start with the biggest folders in the current directory.
du -sh ./* 2>/dev/null | sort -h
Flush macOS DNS Cache
Changed DNS but your Mac still visits the old place? Flush the resolver cache.
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
Watch a Log or Build File Update
Need to see whether a file is still changing? Let tail follow it live.
tail -f ./app.log
Search a Log for Errors With Context
A wall of logs is useless until you pull the error and the lines around it.
grep -n -C 2 'ERROR' ./app.log
Check a URL Without Downloading the Page
Before opening a broken page in five browsers, ask the server for headers.
curl -I https://example.com
how to read a fix
Copy less blindly
- Start with the problem statement and check that it matches your situation.
- Read the danger rating and the “when not to use it” note.
- Compare your expected output to the simulated output.
- Copy the command only after the context makes sense.
demo vessel
See example output first
Each demo uses fake files, fake services, and safe fixtures so you can see what the command does before trying it on a real machine.
quality bar
No mystery pastebin commands
Every fix needs a clear use case, safety notes, recovery guidance, and a reproducible example.
Required
Problem, command, danger rating, when not to use it, undo or recovery, expected output, and demo commands.
Distribution
Short demos and transcripts are generated from the same checked lesson data.
Business signal
Useful pages get expanded into deeper guides, videos, and related troubleshooting paths.
project feeds
Machine-readable outputs
These feeds support videos, transcripts, and future tooling. Most readers can ignore them.
Shorts metadata
Titles, captions, target duration, playlist, and voiceover seed text.
LinkedIn post seeds
Hooks, command snippets, questions, and calls to action for engagement testing.
Analytics event contract
Privacy-light events to measure copy clicks, export clicks, lesson depth, and outbound video intent.
roadmap
What is being added next
The library is expanding by problem area: Linux basics, hosting, security triage, macOS, CI/CD, and data workflows.
- publish ten Linux Survival Basics lessons to test search demand
- add web hosting, DNS, SSL, and VPS troubleshooting fixes
- add defensive cybersecurity triage commands
- add Apple/macOS terminal fixes
- add comments with SSO after moderation controls are ready
- collect first-party page, click, copy, scroll, referrer, viewport, and timing events
- expand useful pages into short videos and deeper troubleshooting paths