memtester is a user-space utility for testing the memory subsystem in a computer to determine if it is faulty. It does a good job of finding intermittent faults and non-deterministic faults. It has many tests to help catch borderline memory. memtester should compile and run on any 32- or 64-bit Unix or Unix-like system.
ProcMeter3 is a program for monitoring the system status and other information and displaying it in a series of graphs or as text. Most of the information comes from the /proc filesystem (cpu usage, load average , processes information, memory usage, network traffic, interrupts etc.). Other information is available for other sources (date, time, email status, log file length, disk status etc.). The program is modular and highly configurable.
FTPL (FakeTime Preload Library, aka libfaketime) intercepts various system library calls and tricks programs of your choice into seeing a faked system time without having to change the time system-wide. This can be used for running legacy software with Y2K bugs, testing software for year-2038 compliance, debugging time-related issues such as expired SSL certificates, and using software that ceases to run outside a certain time frame. The faked time can be specified either absolutely or relative to the real current time, and optionally also affects file timestamps. The faked clock continues to run, but can optionally be frozen, slowed down, or made faster. A wrapper script "faketime" simplifies the usage, similar to tools such as fakechroot.
picocom is a minimal dumb-terminal emulation program. It is ideal for embedded systems since its memory footprint is minimal (less than 20K, when stripped). Apart from being a handy little tool, the source distribution includes a simple, easy to use, and thoroughly documented terminal-management library.
Kernel Security Checker is a useful tool to locate attackers residing within a system by employing a direct analysis of the kernel through /dev/kmem and bypassing the hiding techniques of the intruder (kernel static recompilation or use of LKMs). It can find the modified syscalls from userspace, detect the promiscuous interfaces, and find the modifications applied to a protocol.