- Docker vs Virtual Machine: What's the Difference?
Containers share the host's kernel; virtual machines run a whole OS with their own kernel. How that changes isolation, size and startup, and when to use each. - How to Find Large Files on Windows, macOS and Linux
Built-in ways to find what is filling your disk: Windows Storage settings and size: search, PowerShell, macOS Storage, and du, find and ncdu on Linux. - How to Flush the DNS Cache on Windows, macOS and Linux
Clear the DNS cache with ipconfig /flushdns on Windows, killall -HUP mDNSResponder on macOS and resolvectl flush-caches on Linux, plus browser caches. - How to Force Quit a Frozen Program (Windows, macOS, Linux)
Close a frozen app with Task Manager or taskkill on Windows, Option+Command+Esc or kill on macOS, and pkill, xkill or kill -9 on Linux, and why SIGTERM comes first. - How to Generate an SSH Key (Ed25519) on Windows, macOS and Linux
Create an Ed25519 SSH key with ssh-keygen, protect it with a passphrase, load it into ssh-agent, and copy the public key to a server or GitHub, per OS. - How to Install WSL on Windows 10 and 11
Install WSL with one command, pick a Linux distro, check WSL 1 vs 2 with wsl -l -v, move files between Windows and Linux, and fix the virtualization error. - Linux File Permissions and chmod Explained (755, 644, 600)
What rwx and owner, group and others mean, how octal modes like 755, 644 and 600 add up, how to read ls -l, and how chmod u+x and chown change them. - How to Set Environment Variables on Windows, macOS and Linux
Set an environment variable for one session or permanently: set, $env: and setx on Windows, export and ~/.zshrc or ~/.bashrc on macOS and Linux, plus PATH. - How to Zip and Unzip Files from the Command Line
Zip and unzip from the terminal: Compress-Archive and tar on Windows, zip, unzip and tar -czf on macOS and Linux, listing contents, and why zip passwords are weak.
Software & OS
Windows, macOS and Linux tasks: files, permissions, environment variables, SSH, containers.