Unix Users and Groups
A quick reference for how to add and manage UNIX users and groups.
Streaming Compression and Encryption with Tar and OpenSSL
How to do streaming lzma compression and aes-256-cbc encryption with tar and openssl.
The GNU Privacy Guard (GnuPG or GPG) is an implementation of the OpenPGP message format for encrypting and decrypting messages.
mdadm is an easy-to-use software RAID utility for Linux.
This is an overview of how to use iptables for Linux firewall security.