4.1 Linux administration
Every entry filed under Linux administration and its subtopics.
What kind of help
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
8 entries match these filters
- 0320 Fix: address already in use (EADDRINUSE) Something is already listening on the port your program wants. Find the process with lsof or ss, stop it or pick another… Beginner · Fixes an error · Linux, macOS Article Networking & firewalls · Node.js · Processes & ports 15 Oct 2026
- 0342 Which process is using a port, and how to free it Find the program behind a busy port with ss, lsof or fuser, decide whether to stop it properly or kill it, and… Beginner · Step by step · Linux, macOS Article DNS, IP addresses & ports · Networking & firewalls 15 Oct 2026
- 0322 Fix: user is not in the sudoers file sudo refuses because your account is not allowed to use it. Add the user to the sudo group (Debian, Ubuntu) or wheel… Beginner · Fixes an error · Linux, macOS Article Server hardening · Users, sudo & hardening 15 Oct 2026
- 0309 What is RAID? RAID combines several disks into one so data survives a disk failure or is read and written faster. Beginner · Explains an idea · Any system Article Disks, LVM & filesystems 15 Oct 2026
- 0316 Fix: command not found bash: something: command not found means the shell could not find a program with that name in any PATH directory. The usual… Beginner · Fixes an error · Linux, macOS Article Basics · Packages & updates 15 Oct 2026
- 0317 Fix: Permission denied when running a script (chmod +x) bash: ./script.sh: Permission denied means the file exists but you may not execute it. Usually the execute bit is missing; sometimes the… Beginner · Fixes an error · Linux, macOS Article Basics · Users, sudo & hardening 15 Oct 2026
- 0288 What is a daemon or service? A daemon or service is a program that runs in the background all the time, waiting to do its job without a… Beginner · Explains an idea · Any system Article Services & systemd 15 Oct 2026
- 0281 What is a package manager? A package manager is a tool that installs, updates and removes software for you and keeps track of what depends on what. Beginner · Explains an idea · Any system Article Packages & updates 15 Oct 2026