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.
Clonezilla is a partition or disk cloning tool similar to Symantec Ghost. It saves and restores only blocks in use on the hard drive if the file system is supported. For unsupported file systems, dd is used instead. It has been used to clone a 5 GB system to 40 clients in about 10 minutes.
Clam AntiVirus is an anti-virus toolkit designed especially for email scanning on mail gateways. It provides a number of utilities, including a flexible and scalable multi-threaded daemon, a commandline scanner, and a tool for automatic database updates. The core of the package is an anti-virus engine available as a shared library.
The WiKID Strong Authentication System is a highly scalable, secure two-factor authentication system. It is simple to implement and maintain, allows users to be validated automatically, requires no hardware tokens, has a simple API for application support (via Ruby, PHP, Java, COM, Python, etc.), supports multiple domains, and supports replication for fault tolerance and scalability. It also supports mutual /host and transaction authentication, wireless tokens only domains, locked tokens (to your PC), anti-keystroke logger keypad PIN entry, etc.
ZABBIX is an enterprise-class distributed monitoring solution designed to monitor and track performance and availability of network servers, devices, and other IT resources. It supports distributed and Web-based monitoring, auto-discovery, real-time monitoring, SLA assurance, trending, and more.
GroupOffice is a groupware suite that takes your office online, implementing online collaboration and CRM. It allows you to share projects, calendars, files and email online with co-workers and clients. It is easy to use and fully customizable. It also features synchronization with PDAs and Outlook.
The Advanced Bash Scripting Guide is both a reference and a tutorial on shell scripting. This comprehensive book, the equivalent of 1,000+ print pages, covers almost every aspect of shell scripting. It contains 382 profusely commented illustrative examples, a number of tables, and a cross-linked index/glossary. Not just a shell scripting tutorial, this book also provides an introduction to basic programming techniques, such as sorting and recursion. Included scripts are the Game of Life, a Perquackey variant, a Morse code trainer, and an implementation of the Gronsfeld Cipher. This book is suited for both individual study and classroom use. It covers Bash, up to and including version 4.2. Note that users of miniaturized single-board computers running Linux, such as the Raspberry Pi and the Beagle Bone, would find this Guide useful for learning and running Bash scripts to explore and expand the capabilities of these small, but powerful machines.
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.