Linux is a clone of the Unix kernel, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance. It has all the features you would expect in a modern fully-fledged Unix kernel, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and TCP/IP networking.
fio is an I/O tool meant to be used both for benchmark and stress/hardware verification. It has support for 19 different types of I/O engines (sync, mmap, libaio, posixaio, SG v3, splice, null, network, syslet, guasi, solarisaio, and more), I/O priorities (for newer Linux kernels), rate I/O, forked or threaded jobs, and much more. It can work on block devices as well as files. fio accepts job descriptions in a simple-to-understand text format. Several example job files are included. fio displays all sorts of I/O performance information, including complete IO latencies and percentiles. Fio is in wide use in many places, for both benchmarking, QA, and verification purposes. It supports Linux, FreeBSD, NetBSD, OpenBSD, OS X, OpenSolaris, AIX, HP-UX, Android, and Windows.
Snort is a network intrusion detection and prevention system. It is the most widely deployed technology of its kind in the world. It performs detection using a variety of methods including rules-based detection, anomaly detection, and heuristic analysis of network traffic. Its rules language is open source and available to the public as well.
BalanceNG is a modern, IPv6 capable software IP load balancing solution. It is small, fast, and easy to use and set up. It offers session persistence, different distribution methods (Round Robin, Random, Weighted Random, Least Session, Least Bandwidth, Hash, Agent, and Randomized Agent) and a customizable UDP health check agent in source code. It supports VRRP to set up high availability configurations on multiple nodes. It supports SNMP, integrating the BALANCENG-MIB with Net-SNMPD. It implements a very fast in-memory IP-to-location database, allowing powerful location-based server load-balancing.
NoMachine NX is a fast terminal server and desktop virtualization system based on the X11 protocol. NX is an order of magnitude faster than VNC or X11 and can run on bandwidth as narrow as 10 kBit/sec. In addition, NX translates and embeds the MS Windows Terminal Server and VNC protocols into X/NX, enabling users to compress and accelerate remote Windows and VNC sessions. The NX project provides a suite of libraries and X11 proxying agents implementing efficient compression and optimized transport of X11, SMB, IPP, HTTP, and arbitrary protocols like audio and video over the Internet.
The sysstat package contains the sar, sadf, iostat, nfsiostat, cifsiostat, mpstat, and pidstat commands for Linux. The sar command collects and reports system activity information. The statistics reported by sar concern I/O transfer rates, paging activity, process-related activites, interrupts, network activity, memory and swap space utilization, CPU utilization, kernel activities, and TTY statistics, among others. The sadf command may be used to display data collected by sar in various formats. The iostat command reports CPU statistics and I/O statistics for tty devices and disks. The pidstat command reports statistics for Linux processes. The mpstat command reports global and per-processor statistics. The nfsiostat command reports I/O statistics for network filesystems. The cifsiostat command reports I/O statistics for CIFS filesystems.
Pen is a load balancer for "simple" TCP-based protocols such as HTTP or SMTP. It allows several servers to appear as one to the outside. It automatically detects servers that are down and distributes clients among the available servers. This gives high availability and scalable performance.
Berkeley DB (libdb) is a programmatic toolkit that provides embedded database support for both traditional and client/server applications. It includes b+tree, queue, extended linear hashing, fixed, and variable-length record access methods, transactions, locking, logging, shared memory caching, database recovery, and replication for highly available systems. DB supports C, C++, C#, Java, PHP, and Perl APIs. It supports key-value pair (NoSQL), SQL, and Java Object formatted data. It is available for a wide variety of Unix platforms as well as QNX, Android, Mac OS X, and several varieties of Windows.