Servers & Self-Hosting
4 curated resources, easiest first.
ssh-keygen -p changes the passphrase on an existing key without generating a new one, so servers that already trust the key keep working. Use -f to choose a key file other than the default.
SSH refuses config and key files that other users could read or write. The answer sets the config to 600, checks the files belong to you, and includes a table of the correct permissions for the .ssh folder (700), private keys (600) and other files.
Explains RFC 1918, which reserves address blocks (10.x, 172.16-31.x and 192.168.x) for private networks, and how NAT on your router lets every home reuse them. Includes the history of why it works this way.
A detailed explanation of how multi-access-point Wi-Fi works: give every AP the same network name, security type and password, connect them all to the same wired network, and let devices pick the strongest one. It covers the settings that must match and how channels should differ.