A curated list of amazingly awesome open source sysadmin resources.

awesome-list awesome list sysadmin

Tim Owens d7fdde520a Add Linux Malware Detect (LMD)		10 years ago
CONTRIBUTING.md	trying to clarify contribution guidelines	10 years ago
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README.md	Add Linux Malware Detect (LMD)	10 years ago

README.md

Awesome Sysadmin

A curated list of amazingly awesome open source sysadmin resources. You can check out other awesome lists as well. Please read CONTRIBUTING if you wish to add software.

Awesome Sysadmin
Resources
- Blogs
- Books
- Newsletters
- Repositories
- Websites

Automation

Automation build.

Apache Ant - Automation build tool, similar to make, written in Java.
Apache Maven - Build automation tool mainly for Java.
GNU Make - The most popular automation build tool for many purposes.
Gradle - Another open source build automation system.

Backups

Backup software.

Amanda - Client-server model backup tool.
Attic - A deduplicating backup program written in Python.
Bacula - Another Client-server model backup tool.
Bareos - A fork of Bacula backup tool.
Backupninja - Lightweight, extensible meta-backup system.
Backuppc - Client-server model backup tool with file pooling scheme.
Brebis - A fully automated backup checker
Burp - Network backup and restore program.
Duplicity - Encrypted bandwidth-efficient backup using the rsync algorithm.
Elkarbackup - Backup solution based on RSnapshot with a simple web interface
Lsyncd - File Monitor which spawns a process to synchronize the changes (rsync by default).
Rsnapshot - Filesystem Snapshotting Utility.
SafeKeep - Centralized pull-based backup using rdiff-backup.
Snebu – Snapshot backup with global multi-client deduplication and transparent compression.
TarSnap - Secure backup service with an open-source client.
UrBackup - Another client-server backup system.
DREBS - AWS EBS backup script that supports strategies.
ZBackup - A versatile deduplicating backup tool.

ChatOps

Conversation-driven development and management. See http://www.reddit.com/r/chatops for more information.

CloudBot - The simple, fast, expandable, open-source Python IRC bot.
Eggdrop - the world's most popular Open Source IRC bot, designed for flexibility and ease of use, and is freely distributable under the GNU GPL.
Err - a plugin based chatbot designed to be easily deployable, extensible and maintainable.
Hubot - A customizable, life embetterment robot.
Lazlo - A chatops automation framework in Go.
Lita - A robot companion for your company's chat room.

Cloning

Cloning software.

Clonezilla - Partition and disk imaging/cloning program.
Fog - Another computer cloning solution.
Redo Backup - Easy Backup, Recovery and Restore.

Cloud Computing

AppScale - Open source cloud software with Google App Engine compatibility.
Archipel - Manage and supervise virtual machines using Libvirt.
CloudStack - Cloud computing software for creating, managing, and deploying infrastructure cloud services.
Cobbler - Cobbler is a Linux installation server that allows for rapid setup of network installation environments.
Eucalyptus - Open source private cloud software with AWS compatibility.
Mesos - Develop and run resource-efficient distributed systems.
OpenNebula - An user-driven cloud management platform for sysadmins and devops.
OpenStack - Open source software for building private and public clouds.
The Foreman - Foreman is a complete lifecycle management tool for physical and virtual servers. FOSS.

Cloud Orchestration

BOSH - IaaS orchestration platform originally written for deploying and managing Cloud Foundry PaaS, but also useful for general purpose distributed systems.
Cloudify - Open source TOSCA-based cloud orchestration software platform written in Python and YAML.
CloudSlang - Flow-based orchestration tool for managing deployed applications, with Docker capabilities.
Juju - Cloud orechestration tool which manages services as charms, YAML configuration and deployment script bundles.
MCollective - Ruby framework to manage server orchestration, developed by Puppet labs.
Overcast - Deploy VMs across different cloud providers, and run commands and scripts across any or all of them in parallel via SSH.
Rundeck - Simple orchestration tool.
Salt - Fast, scalable and flexible systems management software written in Python/ZeroMQ.
StackStorm - Event Driven Operations and ChatOps platform for infrastructure management. Written in Python

Cloud Storage

git-annex assistant - A synchronised folder on each of your OSX and Linux computers, Android devices, removable drives, NAS appliances, and cloud services.
ownCloud - Provides universal access to your files via the web, your computer or your mobile devices.
Seafile - Another Open Source Cloud Storage solution.
SparkleShare - Provides cloud storage and file synchronization services. By default, it uses Git as a storage backend.
Swift - A highly available, distributed, eventually consistent object/blob store.
Syncthing - Open Source system for private, encrypted and authenticated distribution of data.

Code Review

Web Based collaborative code review system.

Gerrit - Based on the Git version control, it facilitates software developers to review modifications to the source code and approve or reject those changes.
Phabricator - Code review tool build by facebook and used by WikiMedia, FB, dropbox etc. Comes with an integrated wiki, bug tracker, VC integration and a CLI tool called arcanist.
Review Board - Available as free software under the MIT License.

Collaborative Software

Collaborative software or groupware suites.

Citadel/UX - Collaboration suite (messaging and groupware) that is descended from the Citadel family of programs.
EGroupware - Groupware software written in PHP.
Horde Groupware - PHP based collaborative software suite that includes email, calendars, wikis, time tracking and file management.
Kolab - Another groupware suite.
SOGo - Collaborative software server with a focus on simplicity and scalability.
Zimbra - Collaborative software suite, that includes an email server and web client.

Configuration Management Database

Configuration management database (CMDB) software.

i-doit - Open Source IT Documentation and CMDB.
iTop - Complete open source, ITIL, web based service management tool.
Ralph - Asset management, DCIM and CMDB system for large Data Centers as well as smaller LAN networks.
Sicekit - The systems & infrastructure encyclopaedia toolkit (based on mediawiki).
Clusto - Helps you keep track of your inventory, where it is, how it's connected, and provides an abstracted interface for interacting with the elements of the infrastructure.
Collins - At Tumblr, it's the infrastructure source of truth and knowledge.

Configuration Management

Configuration management tools.

Ansible - It's written in Python and manages the nodes over SSH.
CFEngine - Lightweight agent system. Configuration state is specified via a declarative language.
Chef - It's written in Ruby and Erlang and uses a pure-Ruby DSL.
Pallet - Infrastructure definition, configuration and management via a Clojure DSL.
Puppet - It's written in Ruby and uses Puppet's declarative language or a Ruby DSL.
Salt - It's written in Python.
Slaughter - It's written in Perl.

Build and software organization tools

Build and software organization tools.

EasyBuild - EasyBuild builds software and modulefiles for High Performance Computing (HPC) systems in an efficient way.
environment-modules Tcl - .
environment-modules Lmod - Lmod is a Lua based module system that easily handles the MODULEPATH Hierarchical problem.
environment-modules Tcl/C - The Environment Modules package provides for the dynamic modification of a user's environment via modulefiles.
HPCBIOS - HPCBIOS is an effort to setup a common, well-documented and reproducible, environment spanning across multiple HPC systems & sites, inclusive of documentation.

Continuous Integration & Continuous Deployment

Continuous integration/deployment software.

Buildbot - Python-based toolkit for continuous integration.
Drone - Continuous integration server built on Docker and configured using YAML files.
GitLab CI - Based off of ruby. They also provide GitLab, which manages git repositories.
Go - Open source continuous delivery server.
Jenkins - An extendable open source continuous integration server.

Control Panels

Web hosting and server control panels

Ajenti - Control panel for Linux and BSD.
Cockpit - New multi-server web interface for Linux servers written in C.
Feathur - VPS Provisioning and Management Software.
Froxlor - Easy to use panel for Linux with Nginx and PHP-FPM support.
ISPConfig - Hosting control panel for Linux.
Sentora - Control panel for Linux, BSD, and Windows based on ZPanel.
VestaCP - Hosting panel for Linux but with Nginx.
Virtualmin - Control panel for Linux based on webmin.
Webmin - Linux server control panel.
ZPanel - Control panel for Linux, BSD, and Windows.

Deployment Automation

Tools and scripts to support deployments to your servers.

Capistrano - Deploy your application to any number of machines simultaneously, in sequence or as a rolling set via SSH (rake based).
Fabric - Python library and cli tool for streamlining the use of SSH for application deployment or systems administration tasks.
Mina - Really fast deployer and server automation tool (rake based).
Rocketeer - PHP task runner and deployment tool.
Vlad the Deployer - Deployment automation (rake based).

Distributed Filesystems

Network distributed filesystems.

Ceph - Distributed object store and file system.
DRBD - Distributed Replicated Block Device.
LeoFS - Unstructured object/data storage and a highly available, distributed, eventually consistent storage system.
GlusterFS - Scale-out network-attached storage file system.
HDFS - Distributed, scalable, and portable file-system written in Java for the Hadoop framework.
Lustre - A type of parallel distributed file system, generally used for large-scale cluster computing.
MooseFS - Fault tolerant, network distributed file system.
MogileFS - Application level, network distributed file system.
OpenAFS - Distributed network file system with read-only replicas and multi-OS support.
TahoeLAFS - secure, decentralized, fault-tolerant, peer-to-peer distributed data store and distributed file system.
XtreemFS - XtreemFS is a fault-tolerant distributed file system for all storage needs.

DNS

DNS servers.

Bind - The most widely used name server software.
djbdns - A collection of DNS applications, including tinydns.
Designate - DNS REST API that support several DNS servers as its backend.
dnsmasq - A lightweight service providing DNS, DHCP and TFTP services to small-scale networks.
Knot - High performance authoritative-only DNS server.
NSD - Authoritative only, high performance, simple name server.
PowerDNS - DNS server with a variety of data storage back-ends and load balancing features.
Unbound - Validating, recursive, and caching DNS resolver.
Yadifa - Lightweight authoritative Name Server with DNSSEC capabilities powering the .eu top-level domain.

Editors

Open source code editors.

Atom - A hackable text editor from Github.
Brackets - Open source code editor for web designers and front-end developers.
Eclipse - IDE written in Java with an extensible plug-in system.
Geany - GTK2 text editor.
GNU Emacs - An extensible, customizable text editor-and more.
Haroopad - Markdown editor with live preview.
ICEcoder - Code editor awesomeness, built with common web languages.
jotgit - Git-backed real-time collaborative code editing.
[KDevelop] (https://www.kdevelop.org/) - An open source IDE by the people behind KDE.
Light Table - The next generation code editor.
Lime - Aims to provide an open source solution to Sublime Text
TextMate - A graphical text editor for OS X.
Vim - A highly configurable text editor built to enable efficient editing.

IT Asset Management

IT Assets Management software.

GLPI - Information Resource-Manager with an additional Administration Interface.
OCS Inventory NG - Enables users to inventory their IT assets.
RackTables - Datacenter and server room asset management like document hardware assets, network addresses, space in racks, networks configuration.
Ralph - Asset management, DCIM and CMDB system for large Data Centers as well as smaller LAN networks.
Snipe IT - Asset & license management software.

LDAP

LDAP servers.

389 Directory Server - Developed by Red Hat.
Apache Directory Server - Apache Software Foundation project written in Java.
Fusion Directory - Improve the Management of the services and the company directory based on OpenLDAP.
OpenDJ - Fork of OpenDS.
OpenDS - Another directory server written in Java.
OpenLDAP - Developed by the OpenLDAP Project.

Log Management

Log management tools: collect, parse, visualize ...

Elasticsearch - A Lucene Based Document store mainly used for log indexing, storage and analysis.
Fluentd - Log Collector and Shipper.
Flume - Distributed log collection and aggregation system.
Graylog2 - Pluggable Log and Event Analysis Server with Alerting options.
Heka - Stream processing system which may be used for log aggregation.
Kibana - Visualize logs and time-stamped data.
Logstash - Tool for managing events and logs.
Octopussy - Log Management Solution (Visualize / Alert / Report).

Mail Clients

Claws Mail - Old school email client (and news reader), based on GTK+.
Mutt - Small but very powerful text-based mail client.
Thunderbird - Free email application that's easy to set up and customize.

Webmail

Webmail applications.

Mailpile - A modern, fast web-mail client with user-friendly encryption and privacy features.
Roundcube - Browser-based IMAP client with an application-like user interface.
SquirrelMail - Another browser-based IMAP client.

Mail Servers

Software for setting up mail servers.

MDA (IMAP/POP3)

Mail Delivery Agents (IMAP/POP3 software).

Courier IMAP/POP3 - Fast, scalable, enterprise IMAP and POP3 server.
Cyrus IMAP/POP3 - Intended to be run on sealed servers, where normal users are not permitted to log in.
Dovecot - IMAP and POP3 server written primarily with security in mind.
Qpopper - One of the oldest and most popular server implementations of POP3.

MTA (SMTP)

Mail Transfer Agents (SMTP servers).

Exim - Message transfer agent (MTA) developed at the University of Cambridge.
Haraka - A high-performance, pluginable SMTP server written in JavaScript.
MailCatcher - Ruby gem that deploys a simply SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development.
Maildrop - Open Source disposable email SMTP server, also useful for development.
OpenSMTPD - Secure SMTP server implementation from the OpenBSD project.
Postfix - Fast, easy to administer, and secure Sendmail replacement.
Qmail - Secure Sendmail replacement.
Sendmail - Message transfer agent (MTA).

complete solutions

Software for simple deployment of a mail server, e.g. for inexperienced or impatient admins.

Mail-in-a-Box - Take back control of your email with this easy-to-deploy mail server in a box.
iRedMail - Full-featured mail server solution based on Postfix and Dovecot.
Citadel - Feature packed, easy, versatile, and powerful mail server, thanks to exclusive "rooms" based architecture.

Monitoring

Monitoring software.

Alerta - Distributed, scaleable and flexible monitoring system.
Cacti - Web-based network monitoring and graphing tool.
Cabot - Monitoring and alerts, similar to PagerDuty.
check_mk - Collection of extensions for Nagios.
Dash - A low-overhead monitoring web dashboard for a GNU/Linux machine.
Flapjack - Monitoring notification routing & event processing system.
Icinga - Fork of Nagios.
LibreNMS - fork of Observium.
Monit - Small Open Source utility for managing and monitoring Unix systems.
Munin - Networked resource monitoring tool.
Naemon - Network monitoring tool based on the Nagios 4 core with performance enhancements and new features.
Nagios - Computer system, network and infrastructure monitoring software application.
Node-Bell - Real-time anomalies detection for periodic time series, metrics monitor.
Observium - SNMP monitoring for servers and networking devices. Runs on linux.
OMD - The Open Monitoring Distribution.
Riemann - Flexible and fast events processor allowing complex events/metrics analysis.
Sensu - Open source monitoring framework.
Sentry - Application monitoring, event logging and aggregation.
Shinken - Another monitoring framework.
Thruk - Multibackend monitoring web interface with support for Naemon, Nagios, Icinga and Shinken.
Xymon - Network monitoring inspired by Big Brother.
Zabbix - Enterprise-class software for monitoring of networks and applications.
Zenoss - Application, server, and network management platform based on Zope.

Metric & Metric Collection

Metric gathering and display software.

Collectd - System statistic collection daemon.
Collectl - High precision system performance metrics collecting tool.
Dashing - Ruby gem that allows for rapid statistical dashboard development. An all HTML5 approach allows for big screen displays in data centers or conference rooms.
Diamond - Python based statistic collection daemon.
Facette - Time series data visualization and graphing software written in Go.
Freeboard - A damn-sexy front-end real-time dashboard. Transforms raw JSON into delicious UI.
Ganglia - High performance, scalable RRD based monitoring for grids and/or clusters of servers. Compatible with Graphite using a single collection process.
Grafana - A Graphite & InfluxDB Dashboard and Graph Editor.
Graphite - Open source scalable graphing server.
InfluxDB - Open source distributed time series database with no external dependencies.
KairosDB - Fast distributed scalable time series database, fork of OpenTSDB 1.x.
OpenTSDB - Store and server massive amounts of time series data without losing granularity.
Packetbeat - Captures network traffic and displays it in a custom Kibana dashboard for easy viewing.
Prometheus - An open-source service monitoring system and time series database.
RRDtool - Open source industry standard, high performance data logging and graphing system for time series data.
Statsd - Application statistic listener.

Network Configuration Management

Network configuration management tools.

GestióIP - An automated web based IPv4/IPv6 IP Address Management tool.
Oxidized - A modern take on network device configuration monitoring with web interface and GIT storage.
RANCID - Monitors network device's configuration and maintain history of changes.
rConfig - Another network device configuration management tool.
trigger - Robust network automation toolkit written in Python.

Newsletters

Newsletter software.

DadaMail - Mailing List Manager, written in Perl.
phpList - Newsletter manager written in PHP.

NoSQL

NoSQL databases.

Column-Family
- Apache HBase - Hadoop database, a distributed, big data store.
- Cassandra - Distributed DBMS designed to handle large amounts of data across many servers.
- Hypertable - C++ based BigTable-like DBMS, communicates through Thrift and runs either as stand-alone or on distributed FS such as Hadoop.
Document Store
- CouchDB - Ease of use, with multi-master replication document-oriented database system.
- ElasticSearch - Java based database, popular with log aggregation, and email archiving projects.
- MongoDB - Another document-oriented database system.
- RavenDB - Document based database with ACID/Transactional features.
- RethinkDB - Open source distributed document store database, focuses on JSON.
Graph
- FlockDB - Twitter's distributed, fault-tolerant graph database.
- Neo4j - Open source graph database.
Key-Value
- LevelDB - Google's high performance key/value database.
- Redis - Networked, in-memory, key-value data store with optional durability.
- Riak - Another fault-tolerant key-value NoSQL database.

Comparison of NoSQL servers: http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis

Packaging

fpm - Versatile multi format package creator.
omnibus-ruby - Full stack, cross distro packaging software (Ruby).
packman - Full stack, cross distro packaging software (Python).
tito - Builds RPMs for git-based projects.

Queuing

ActiveMQ - Open source java message broker.
BeanstalkD - A simple, fast work queue.
Gearman - Fast multi-language queuing/job processing platform.
Kafka - Extremely high performance publish/subscribe message system.
NSQ - A realtime distributed messaging platform.
RabbitMQ - Robust, fully featured, cross distro queuing system.
ZeroMQ - Lightweight queuing system.

RDBMS

Relational DBMS.

Firebird - True universal open source database.
Galera - Galera Cluster for MySQL is an easy-to-use high-availability solution with high system up-time, no data loss, and scalability for future growth.
MariaDB - Community-developed fork of the MySQL.
MySQL - Most popular RDBMS server.
Percona Server - Enhanced, drop-in MySQL replacement.
PostgreSQL - Object-relational database management system (ORDBMS).
PostgreSQL-XL - Scalable Open Source PostgreSQL-based database cluster.
SQLite - Library that implements a self-contained, serverless, zero-configuration, transactional SQL DBS.

Security

Security tools.

Blackbox - Safely store secrets in Git/Mercurial. Provides tooling to automatically encrypt secrets like passwords.
Denyhosts - Thwart SSH dictionary based attacks and brute force attacks.
Fail2Ban - Scans log files and takes action on IPs that show malicious behavior.
fwknop - Protects ports via Single Packet Authorization in your firewall.
Glastopf - A low-interaction web application honeypot to emulate vulnerabilities and gather attack data.
Kippo - A medium-interaction SSH honeypot, mostly used as a standalone SSH daemon with a configurable Filesystem sandbox.
Linux Malware Detect - A malware scanner for Linux designed around the threats faced in shared hosted environments.
OSSEC - OSSEC is a HIDS that performs log analysis, FIM, rootkit detection, and much more.
OSQuery - Query your servers status and info using a SQL like interface.
pfSense - Firewall and Router FreeBSD distribution.
Snort - Snort is a free and open source network intrusion prevention system (NIPS) and network intrusion detection system (NIDS) created by Martin Roesch in 1998.
SpamAssassin - A powerful and popular email spam filter employing a variety of detection technique.

Service Discovery

Consul - Consul is a tool for service discovery, monitoring and configuration.
Doozerd - Doozer is a highly-available, completely consistent store for small amounts of extremely important data.
ZooKeeper - ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.

Software Containers

Operating system–level virtualization.

Bitnami - Produces open source installers or software packages for web applications and development stacks as well as virtual appliances.
Docker - Open platform for developers and sysadmins to build, ship, and run distributed applications.
LXC - Userspace interface for the Linux kernel containment features.
OpenVZ - Container-based virtualization for Linux.

SSH

SSH tools.

Advanced SSH config - Enhances ssh_config file capabilities, completely transparent.
autossh - Automatically respawn ssh session after network interruption.
Cluster SSH - Controls a number of xterm windows via a single graphical console.
DSH - Dancer's shell / distributed shell - Wrapper for executing multiple remote shell commands from one command line.
Mosh - The mobile shell.
parallel-ssh - Provides parallel versions of OpenSSH and related tools.
SSH Power Tool - Execute commands and upload files to many servers simultaneously without using pre-shared keys.
sshrc - sources ~/.sshrc on your local computer after logging in remotely.
stormssh - A command line tool to manage SSH connections.

Statistics

Analytics software.

Analog - Logfile Analyser.
AWStats - Generates web, streaming, ftp or mail server statistics graphically.
GoAccess - Real-time web log analyzer and interactive viewer that runs in a terminal.
Open Web Analytics - Add web analytics to websites using JS, PHP or REST APIs.
Piwik - Web analytics application.
Webalizer - Fast web server log file analysis.

Status Pages

Cachet - An open source status page system written in PHP.

Ticketing systems

Web-based ticketing system.

Bugzilla - General-purpose bugtracker and testing tool originally developed and used by the Mozilla project.
Cerb - Group-based e-mail management project.
Flyspray - Web-based bug tracking system written in PHP.
MantisBT - Web-based bug tracking system.
osTicket - Simple support ticket system.
OTRS - Trouble ticket system for assigning tickets to incoming queries and tracking further communications.
Request Tracker - Ticket-tracking system written in Perl.
TheBugGenie - Ticket system with extensive user rights system.

Troubleshooting

Troubleshooting Tools.

mitmproxy - A Python tool used for intercepting, viewing and modifying network traffic. Invaluable in troubleshooting certain problems.
Sysdig - Capture system state and activity from a running Linux instance, then save, filter and analyze.
Trinity Rescue Kit - Linux Live CD for general computer troubleshooting.
Wireshark - The world's foremost network protocol analyzer.

Project Management

Web-based project management and bug tracking systems.

ChiliProject - Fork of Redmine.
GitBucket Clone of GitHub written in Scala; single jar install.
GitLab - Clone of GitHub written in Ruby.
Gogs - Self-hosted Git service written in Go.
OpenProject - Project collaboration with open source.
Phabricator Written in PHP.
Redmine - Written in ruby on rails.
Taiga - Agile, Free, Open Source Project Management Tool based on the Kanban and Scrum methods.
The Bug Genie - Written in PHP.
Trac - Written in python.

Version control

Software versioning and revision control.

Fossil - Distributed version control with built-in wiki and bug tracking.
Git - Distributed revision control and source code management (SCM) with an emphasis on speed.
GNU Bazaar - Distributed revision control system sponsored by Canonical.
Mercurial - Another distributed revision control.
Subversion - Client-server revision control system.

Virtualization

Virtualization software.

Archipel - XMPP based virtualization management platform.
Ganeti - Cluster virtual server management software tool built on top of KVM and Xen.
KVM - Linux kernel virtualization infrastructure.
OpenNebula - Flexible enterprise cloud made simple.
oVirt - Manages virtual machines, storage and virtual networks.
Packer - A tool for creating identical machine images for multiple platforms from a single source configuration.
Proxmox VE - Complete open source virtualization management solution.
QEMU - QEMU is a generic and open source machine emulator and virtualizer.
Vagrant - Tool for building complete development environments.
VirtualBox - Virtualization product from Oracle Corporation.
Xen - Virtual machine monitor for 32/64 bit Intel / AMD (IA 64) and PowerPC 970 architectures.

VPN

VPN software.

OpenVPN - Uses a custom security protocol that utilizes SSL/TLS for key exchange.
Pritunl - OpenVPN based solution. Easy to set up.
SoftEther - Multi-protocol software VPN with advanced features
sshuttle - Poor man's VPN.
strongSwan - Complete IPsec implementation for Linux.
tinc - Distributed p2p VPN.

XMPP

XMPP servers.

ejabberd - XMPP instant messaging server written in Erlang/OTP.
Metronome IM - Fork of Prosody IM.
MongooseIM - Fork of ejabberd.
Openfire - Real time collaboration (RTC) server.
Prosody IM - XMPP server written in Lua.
Tigase - XMPP server implementation in Java.

XMPP Web Clients

Candy - Multi user XMPP client written in Javascript.
Kaiwa - Web based chat client in the style of common paid alternatives.
Lets-Chat - A self hosted chat suite written in Node.

Web

Web servers.

Apache - Most popular web server.
Cherokee - Lightweight, high-performance web server/reverse proxy.
Lighttpd - Web server more optimized for speed-critical environments.
Nginx - Reverse proxy, load balancer, HTTP cache, and web server.
uWSGI - The uWSGI project aims at developing a full stack for building hosting services.

Web Performance

HAProxy - Software based load Balancing, SSL offloading and performance optimization, compression, and general web routing.
Varnish - HTTP based web application accelerator focusing on optimizing caching and compression.

Wikis

Wiki software.

DokuWiki - Simple to use and highly versatile wiki that doesn't require a database.
Gollum - A simple, Git-powered wiki with a sweet API and local frontend.
ikiwiki - A wiki compiler.
MDwiki - Wiki completely built in HTML5/Javascript and runs 100% on the client
Mediawiki - Used to power Wikipedia.
MoinMoin - An advanced, easy to use and extensible WikiEngine with a large community of users.
Ōlelo Wiki - A a wiki that stores pages in a Git repository.
TiddlyWiki - Complete interactive wiki in JavaScript.

Resources

Various resources, such as books, websites and articles, for improving your skills and knowledge.

Blogs

Code as Craft - Etsy's Ops blog, lots of technical posts.
DevOpsGuys - Devops consultants who blog about operations.
Rackspace Developers - Slightly biased blog with lots of Devops Topics.

Books

Sysadmin related books.

The Linux Command Line - A book about the Linux command line by William Shotts.
The Phoenix Project: A Novel about IT, DevOps, and Helping Your Business Win - How DevOps techniques can fix the problems that happen in IT organizations.
The Practice of System and Network Administration - The first and second editions describes the best practices of system and network administration, independent of specific platforms or technologies.
The Visible Ops Handbook: Implementing ITIL in 4 Practical and Auditable Steps - Is a methodology designed to jumpstart implementation of controls and process improvement.
UNIX and Linux System Administration Handbook - Approaches system administration from a practical perspective.

Newsletters

Servers for Hackers - Newsletter for programmers who find themselves needing to know their way around a server.
Web Operations Weekly - A weekly newsletter on Web operations, infrastructure, performance, and tooling, from the browser down to the metal.

Repositories

Software package repositories.

AlternativeTo - Find alternatives to software you know and discover new software.

Debian-based distributions

Dotdeb - Repository with LAMP updated packages for Debian.

RPM-based distributions

ElRepo - Community Repo for Enterprise Linux (RHEL, CentOS, etc).
EPEL - Repository for RHEL and compatibles (CentOS, Scientific Linux).
Remi - Repository with LAMP updated packages for RHEL/Centos/Fedora.
Software Collections - Community Release of Red Hat Software Collections. Provides updated packages of Ruby, Python, etc. for CentOS/Scientific Linux 6.x.

Websites

Useful sysadmin related websites.

Ops School - Comprehensive program that will help you learn to be an operations engineer.
Digital Ocean Tutorials - A surprisingly vast resource for getting the basics of certain applications, tools, or even systems administration topics.

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International license.