Vim is a text editor that is very simple and lightweight, but extremely powerful. This article provides some tips and how-to's to get started.
Bash is the "Born Again SHell" (BASH) written by Brian Fox and is the default shell on many unix systems.
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.