From Free Open Source Software
Good FOSS system software -- the underlying operating systems, middleware, and utilities -- are collected below:
- Puppet - automated installation, configuration, management, etc.
- Amanda - most widely used FOSS backup software.
- Bacula - second most widely used FOSS backup software.
 Bug Tracking & Management
- BugZilla - standard FOSS bug management app, traces its heritage back to Mozilla Netscape.
- Entomologist - coordination of multiple bug trackers.
- Memcached - memory caching.
 Certificates - Digital, SSL
- Dogtag - enterprise-class Certificate Authority (CA), hardened by real-world deployments, supporting OCSP, smartcards, and more.
- easy-rsa - OpenVPN utility to build and manage a PKI CA, create a root certificate authority, and request and sign certificates, including sub-CAs,
- EJBCA - Certificate Authority and OCSP support, using Java, high performance, highly scalable, platform independent.
- OpenCA - robust, out-of-the-box Certification Authority with full-strength cryptography, based on openLDAP, OpenSSL, Apache Project, and Apache mod_ssl.
- OpenSSL - robust, commercial-grade, toolkit implementing Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1), and a full cryptography library.
- r509 - Ruby gem using OpenSSL for creation of signed certificates, CSRs, and revocation (CRL/OCSP), for full RFC 3280/5280 certificate authority enterprise use.
- TinyCA2 - fork of the no longer maintained TinyCA, manages a certification authority and x509 certificates as a frontend to OpenSSL, including subCAs for more complex setups.
- XCA - for creating and managing X.509 certificates, certificate requests, RSA, DSA and EC private keys, Smartcards, CRLs, and sub-CAs.
 Cloud Computing
- See Cloud Computing page.
 Collaboration Server
- 7-Zip - standard gzip, zip, other compression.
 Configuration Management
- Git - highly scalable, developed by Linux creator Linus Torvalds.
- Subversion - one of the first FOSS CM apps.
 Cross Language Development
- Finagle - Twitter network stack for the JVM to build asynchronous RPC clients and servers in any JVM hosted language.
- Drizzle - MySQL fork.
- HyperTable - very high scalability Hadoop compatible distributed database.
- MariaDB - MySQL replacement.
- Membrane SOA Registry - a registry for SOA services.
- MongoDB - scalable NoSQL database.
- MySQL - popular relational database.
- PostgreSQL - standard FOSS enterprise relational database, very highly scalable.
- Neo4j - high-performance, NOSQL graph database.
- Perst - object oriented embedded database.
- RavenDB - document database.
- Redis - in-memory key value data store.
- Riak - fault tolerant distributed database.
- SQLite - light-weight relational database.
- Voldemort - distributed database.
 Database Management
- phpMyAdmin - one of the first GUI tools for DB management.
 Data-Center Management
- DWR - Ajax Java library.
- Bootstrap - Twitter framework for web development.
- Jaxar - Ajax server.
- Ruby on Rails - supports very rapid web development.
- FreePascal - A FOSS Pascal editor/compiler like Turbo Pascal that runs on multiple operating systems (Linux/FreeBSD/Mac OS X/iOS/Darwin/DOS/Windows ...) and architectures (Intel x86, AMD64/x86-64, PowerPC, PowerPC64, SPARC, and ARM).
- Lazarus - Lazarus is a GUI editor like Delphi and uses the FreePascal Compiler. Write once compile anywhere.
 Directory Services
- OpenLDAP - standard FOSS Light-weight Directory Access Protocol (LDAP) solution.
 Disk Partitioning
 Distributed Computing (High Scalability)
- Cassandra - distributed data replication and fault tolerance.
- Hadoop - processing of very large data sets across many computers.
- Mesos - application resource management across clusters.
- Spark - high scalability distributed data analytics.
- Storm - distributed very large data set processing.
 Domain Name System (DNS)
- BIND - manages the relationships between domain names and IP addresses, pretty much runs the Internet.
- Linux drivers - drivers for printers, scanners, and other hardware devices for Linux operating systems.
- Davmail - Microsoft Exchange connector for almost any client.
- Dovecot - standard FOSS email server with IMAP, POP3 support.
- DSPAM - content-based adaptive spam filter for multi-user enterprise systems.
- OpenDKIM - DKIM (Domain Keys Identified Mail) sender authentication system (RFC6376), includes Author Domain Signing Practises (ADSP, RFC5617), Vouch By Reference (VBR, RFC5518), and Authorized Third Party Signatures protocol (ATPS, RFC6541).
- Postfix - standard FOSS Mail Transfer Agent (MTA).
 File Encryption
- End-to-End - email encryption plugin for Chrome web browser.
- FreeOTFE - old FOSS on-the-fly disk file encryption.
 Enterprise Service Bus
- HylaFax - fax send, receive, route to email.
 File Synchronization
 File Systems
- Ceph - distributed object store and file system.
 File Transfer Protocol (FTP)
 Geographic Information Systems
 Groupware Synchronization
- SyncEvolution - synchronizing with Evolution email / calendar / contacts app.
 Messaging Systems
- RabitMQ - application messaging.
- Red5 server - flash video emulator.
- Tizen - device API for HTML5.
 Natural Language Processing (NLP)
- Linux Wireless - IEEE-802.11 subsystem.
- OpenDayLight - software defined networking (SDN).
- Samba - connection of Linux and Microsoft Windows networking, file systems, printers.
 Network Management
- Nagios - standard FOSS monitoring and alerting software.
 Network Monitoring
- WireShark - IP network packet inspection.
 Operating Systems
- Contiki - lightweight OS for the "Internet of things".
- Linux - FOSS version of Unix, now the standard and most widely used server operating system.
- Red Hat - first commercially supported Linux operating system (1993).
- Tails - Secure Linux bootable from USB with privacy tools builtin.
- Ubuntu - most widely used FOSS desktop operating system.
 Operating Systems Embedded
 Operating System Emulation
- Wine - Windows emulator on Linux, can run some but not all versions of a lot of Windows software.
 Operating System Virtualization
- OpenVZ - Linux kernel parallelization.
 Password Utilities
- Offline Windows Password & Registry Editor, Bootdisk / CD - Win NT 3.5 through Windows 8.1 (GPL)
- ophcrack - Windows password cracker using rainbow tables (Apache 2, GPL2)
- Liferay - mobile content development.
 Proxy Servers
- Nginx - HTTP and reverse proxy server, and mail proxy server.
 Security Software
- Barada - two factor password authentication.
- Kerberos - standard FOSS software for secure authentication of users and software.
- monkeysphere - management of networks of trust.
- OpenVPN - standard FOSS software for virtual private networks.
- CyaSSL - certificates.
- Android - standard FOSS smartphone software from Google.
- Funambol - standard FOSS smartphone system and software communications integration software.
 Spam and Anti-Virus Protection
- ClamAV - standard FOSS anti-virus tool, mainly used to clean Windows viruses from email passing through.
- ClamWin - ClamAV version for Windows computers.
- dkim-milter - legitimate email authentication support.
- domainkeys-milter - legitimate email authentication support.
- DSPAM - standard FOSS spam blocking software.
- StatsD - front-end proxy for the Graphite/Carbon metrics and graphing server.
 Storage Management
- FreeNAS - Network Attached Storage (NAS) management.
- OpenFiler - NAS and SAN storage appliance.
 System Cloning
 System Integration
- Chef - automation of application management and configuration.
 Systems Management
- Spacewalk - Linux content provisioning and monitoring.
- sysdig - capture and analyze Linux instance state information.
- ZooKeeper - centralized maintenance of system configuration data, Apache project.
- Chaos Monkey - random process termination testing (from Netflix).
- Funkload - web application testing.
- HtmlUnit - GUI-less web emulator for testing from Java.
- Iago - load generator for performance testing.
- Selenium - automated web testing.
- StressLinux - hardware stress testing.
- Zipkin - web service response time profiling.
- WebM - an open web media project developing a high-quality, open video format.
 Virtual Desktop
- FreeNX - the original FOSS NX server.
- neatx - an NX server version from Google.
- SPICE - NX software from Redhat.
- x2go - x-windows remote access.
 Web Server
- Apache Web Server - the first and now standard FOSS website server, runs most of the world's websites, provided an early proof of the superior performance and robustness of a FOSS application.