$ Linux One Liners

linux fixes you can inspect first

Fix the Linux problem in front of you.

Short, copyable commands for Linux, hosting, server, and terminal problems. Every published fix includes safety notes, when not to use it, and example output so you can inspect the command before you run it.

Search Linux fixes

Try disk full, nginx 502, ssh failed login, chmod, or find large files.

Current library

  • 347commands
  • Read-onlyfirst
  • Safetynotes
  • Exampleoutput

start with common problems

What broke?

Disk full Logs Nginx SSH Permissions Backups

topics

Browse broad command areas

21 fixes Inspection first

Web Server Rescue

Small checks that separate DNS, TLS, Nginx, and app failures.

4 fixes Inspection first

Dangerous Commands

Commands worth understanding before copying from the internet.

69 fixes Inspection first

Cybersecurity Triage

Defensive commands for checking exposure, logs, permissions, and suspicious activity.

133 fixes Inspection first

Hosting Operations

Web hosting, SSL, DNS, Nginx, deployment, backups, and VPS management.

10 fixes Inspection first

Apple Terminal

macOS and Apple-adjacent terminal workflows for developers and power users.

verified fixes

Start here

A focused entry set from the 347-command library. Use problem hubs when you are starting from a symptom.

Linux Survival Basics Can be slow

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
Linux Survival Basics Can be slow

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
Linux Survival Basics Can be slow

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
Linux Survival Basics Can be slow

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
Dangerous Commands Dry run

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'
Linux Survival Basics Read-only

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
Linux Survival Basics Can be slow

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
Linux Survival Basics Can be slow

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}'
Apple Terminal Can be slow

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
Apple Terminal Stops processes

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

how to read a fix

Copy less blindly

  1. Start with the problem statement and check that it matches your situation.
  2. Read the system impact and the “when not to use it” note.
  3. Compare your expected output to the example output.
  4. Copy the command only after the context makes sense.

cert practice

Practice real command-line habits

Linux One Liners is useful for unofficial LPIC-1, LFCS, and Linux+ style study because it focuses on the commands people actually need to inspect files, logs, services, packages, permissions, users, storage, and network behavior.

Independent study support only. This site is not affiliated with, endorsed by, or approved by LPI, The Linux Foundation, CompTIA, or any certification provider. No exam dumps and no real exam questions.

LPIC-1 command practice

GNU/Unix commands, filesystems, permissions, packages, shells, admin tasks, networking, and security basics.

LFCS command practice

Performance-style drills for essential commands, operations, storage, networking, users, groups, and service triage.

Cert-prep hub

Use the maps as a study checklist, not as official training or exam content.

Troubleshooting guides

Step-by-step paths for disk, Nginx, DNS, logs, permissions, rsync, ports, systemd, and beginner cert practice.

Practice tasks

Scenario-driven drills for disk, logs, nginx, DNS, ports, permissions, backups, systemd, packages, memory, and SSH review.

example output

See example output first

Many cards use sample files, local test services, and temporary shell labs so you can see what the command does before trying it on a real machine.

Demo output is inspectable

Where a card includes example output, use it as a sanity check before copying the command into a real shell.

quality bar

No mystery pastebin commands

Every fix needs a clear use case, system-impact notes, recovery guidance, and a reproducible example.

Required

Problem, command, system impact, when not to use it, undo or recovery, expected output, and demo commands.

Defensive focus

The site is about troubleshooting, administration, backups, logs, permissions, services, networking, and safe security hygiene.

No exam dumps

Certification pages are objective-aligned study support, not official training, real exam questions, or provider-endorsed content.