systeminfo.sh is a system information gathering script for Linux. It is non-intrusive and simply gathers information from commands that are already available. It outputs a single file or generates a menu driven Web page. The information includes hostname, software packages, memory, OS information, process information, kernel modules, network routes, socket ports, ulimits, chkconfig, hardware devices, swap, disks, DNS info, top, processor, meminfo, dmesg, cron jobs, network interfaces, and more.
Systraq sends you a daily email listing the state of your system. If critical system files or user access files (e.g. ~/.ssh/authorized_keys) have changed, you'll get an email within a shorter notice. It consists of few very small shell scripts. It can help you implement a (not too strict) security policy.
Tailbeep opens a file (-f), seeks to the end, and watches for a string (-s). If the string is found, a beep is sent to the specified tty (-t) device. You can also daemonize (-d) it. It was written to watch /var/log/messages for the DENY string (to catch anyone trying to break into a firewall), but you can use it to watch any open file that gets appended to. You can also create a log if you like, so you can record the events, in long or short mode. Tailbeep requires write access to one of the tty devices on the console.
tcpick is a textmode sniffer that can track TCP streams and saves the data captured in files or displays them in the terminal. It is useful for picking files in a passive way. It can store all connections in different files, or it can display all the stream on the terminal (using colors too).
The tcpsound utility plays sounds in response to network traffic, making it possible for a user to literally listen to a network. It forks a pseudo terminal in which to run tcpdump, parses that output, and plays a wide variety of user-configurable sounds. By interpreting the output in a pseudo terminal, users can first SSH to a remote host if desired.