Awesome Sysadmin
A curated list of amazingly awesome open source sysadmin resources.

Contributing
Please read CONTRIBUTING (./CONTRIBUTING.md) if you wish to add software.

Table of Contents
⟡ Awesome Sysadmin (#awesome-sysadmin)
  ⟡ Backups (#backups)
  ⟡ Build Automation (#build-automation)
  ⟡ ChatOps (#chatops)
  ⟡ Cloning (#cloning)
  ⟡ Cloud Computing (#cloud-computing)
  ⟡ Cloud Storage (#cloud-storage)
  ⟡ Code Review (#code-review)
  ⟡ Collaborative Software (#collaborative-software)
  ⟡ Configuration Management Database (#configuration-management-database)
  ⟡ Configuration Management (#configuration-management)
  ⟡ Continuous Integration & Continuous Deployment (#continuous-integration--continuous-deployment)
  ⟡ Control Panels (#control-panels)
  ⟡ Deployment Automation (#deployment-automation)
  ⟡ Diagramming (#diagramming)
  ⟡ Distributed Filesystems (#distributed-filesystems)
  ⟡ DNS (#dns)
  ⟡ Editors (#editors)
  ⟡ IT Asset Management (#it-asset-management)
  ⟡ LDAP (#ldap)
  ⟡ Log Management (#log-management)
  ⟡ Mail Servers (#mail-servers)
  ⟡ Messaging (#messaging)
  ⟡ Monitoring (#monitoring)
  ⟡ Metric & Metric Collection (#metric--metric-collection)
  ⟡ Network Configuration Management (#network-configuration-management)
  ⟡ Newsletter (#newsletters)
  ⟡ NoSQL (#nosql)
  ⟡ Packaging (#packaging)
  ⟡ Queuing (#queuing)
  ⟡ RDBMS (#rdbms)
  ⟡ Security (#security)
  ⟡ Service Discovery (#service-discovery)
  ⟡ Software Containers (#software-containers)
  ⟡ SSH (#ssh)
  ⟡ Statistics (#statistics)
  ⟡ Status Pages (#status-pages)
  ⟡ Ticketing systems (#ticketing-systems)
  ⟡ Troubleshooting (#troubleshooting)
  ⟡ Project Management (#project-management)
  ⟡ Version control (#version-control)
  ⟡ Virtualization (#virtualization)
  ⟡ VPN (#vpn)
  ⟡ Web (#web)
  ⟡ Webmails (#webmails)
  ⟡ Wikis (#wikis)
⟡ Resources (#resources)
  ⟡ Blogs (#blogs)
  ⟡ Books (#books)
  ⟡ Newsletters (#newsletters)
  ⟡ Repositories (#repositories)
  ⟡ Websites (#websites)


Backups

Backup software.

⟡ Amanda (http://www.amanda.org/) - Client-server model backup tool.
⟡ Attic (https://attic-backup.org) - A deduplicating backup program written in Python.
⟡ Bacula (http://www.bacula.org) - Another Client-server model backup tool.
⟡ Bareos (http://www.bareos.org) - A fork of Bacula backup tool.
⟡ Barman (http://www.pgbarman.org) - Backup and Recovery Manager for disaster recovery of PostgreSQL servers.
⟡ Backupninja (https://labs.riseup.net/code/projects/backupninja) - Lightweight, extensible meta-backup system.
⟡ Backuppc (http://backuppc.sourceforge.net/) - Client-server model backup tool with file pooling scheme.
⟡ Brebis (http://brebisproject.org) - A fully automated backup checker.
⟡ Bup (https://github.com/bup/bup) - Incremental backups with rolling checksums, git packfiles, de-duplication, and a FUSE filesystem.
⟡ Burp (http://burp.grke.org/) - Network backup and restore program.
⟡ Duplicati (http://www.duplicati.com) - Multiple backends, encryption, web-ui and multi-OS backup tool.
⟡ Duplicity (http://duplicity.nongnu.org/) - Encrypted bandwidth-efficient backup using the rsync algorithm.
⟡ FreeFileSync (http://www.freefilesync.org) - Folder comparison and synchronization tool.
⟡ Lsyncd (https://github.com/axkibe/lsyncd) - File Monitor which spawns a process to synchronize the changes (rsync by default).
⟡ restic (https://github.com/restic/restic) - Fast, secure, efficient backup program 
⟡ Rsnapshot (http://www.rsnapshot.org/) - Filesystem Snapshotting Utility.
⟡ SafeKeep (http://safekeep.sourceforge.net/) - Centralized pull-based backup using rdiff-backup.
⟡ Snebu (http://www.snebu.com/) – Snapshot backup with global multi-client deduplication and transparent compression.
⟡ UrBackup (http://www.urbackup.org/) - Another client-server backup system.
⟡ ZBackup (http://zbackup.org/) - A versatile deduplicating backup tool.

Backup libraries.

⟡ Backup (https://github.com/meskyanichi/backup) - Provides an elegant DSL in Ruby for performing backups on UNIX-like systems.
⟡ DREBS (https://github.com/dojo4/drebs) - AWS EBS backup script that supports strategies.

Build Automation

Build automation tools.

⟡ Apache Ant (https://ant.apache.org/) - Automation build tool, similar to make, written in Java.
⟡ Apache Maven (http://maven.apache.org/) - Build automation tool mainly for Java.
⟡ GNU Make (http://www.gnu.org/software/make/) - The most popular automation build tool for many purposes.
⟡ Gradle (http://gradle.org/) - Another open source build automation system.

ChatOps

Conversation-driven development & management.

⟡ CloudBot (https://github.com/CloudBotIRC/CloudBot) - The simple, fast, expandable, open-source Python IRC bot.
⟡ Eggdrop (http://www.eggheads.org/) - The world's most popular Open Source IRC bot, designed for flexibility and ease of use.
⟡ Err (http://errbot.net/) - A plugin based chatbot designed to be easily deployable, extensible and maintainable.
⟡ Hubot (https://hubot.github.com/) - A customizable, life embetterment robot.
⟡ Lazlo (https://github.com/djosephsen/lazlo) - A chatops automation framework in Go.
⟡ Lita (https://www.lita.io/) - A robot companion for your company's chat room.
⟡ KeyBase (https://www.keybase.io/) - Encrypted chat, cloud and git.

Cloning

Cloning software.

⟡ Clonezilla (http://clonezilla.org/) - Partition and disk imaging/cloning program.
⟡ Fog (http://www.fogproject.org/) - Another computer cloning solution.
⟡ Redo Backup (http://redobackup.org/) - Easy Backup, Recovery and Restore.

Cloud Computing

⟡ AppScale (http:/github.com/AppScale/appscale) - Open source cloud software with Google App Engine compatibility.
⟡ Archipel (http://archipelproject.org/) - Manage and supervise virtual machines using Libvirt.
⟡ CloudStack (http://cloudstack.apache.org/) - Cloud computing software for creating, managing, and deploying infrastructure cloud services.
⟡ Cobbler (http://cobbler.github.io) - Cobbler is a Linux installation server that allows for rapid setup of network installation environments.
⟡ Eucalyptus (https://www.eucalyptus.com/) - Open source private cloud software with AWS compatibility.
⟡ Mesos (http://mesos.apache.org/) - Develop and run resource-efficient distributed systems.
⟡ OpenNebula (http://opennebula.org/) - An user-driven cloud management platform for sysadmins and devops.
⟡ Openshift Origin (https://www.openshift.org/) - Open source upstream of OpenShift, the next generation application hosting platform developed by Red Hat.
⟡ OpenStack (https://www.openstack.org/) - Open source software for building private and public clouds.
⟡ The Foreman (http://theforeman.org/) - Foreman is a complete lifecycle management tool for physical and virtual servers. FOSS.
⟡ Tsuru (http://www.tsuru.io/) - Tsuru is an extensible and open source Platform as a Service software.
⟡ Terraform (https://terraform.io) - Terraform allows you to practice infrastructure as code and is commonly used for AWS/GCE.

Cloud Orchestration

⟡ BOSH (http://docs.cloudfoundry.org/bosh/) -  IaaS orchestration platform originally written for deploying and managing Cloud Foundry PaaS, but also useful for general purpose distributed systems.
⟡ Ansible (http://www.ansible.com) - Contains modules for controlling many types of cloud resources.
⟡ Cloudify (http://cloudify.co/) -  Open source TOSCA-based cloud orchestration software platform written in Python and YAML.
⟡ consul (http://www.consul.io/) - It is a tool for discovering and configuring services in your infrastructure.
⟡ doozerd (https://github.com/ha/doozerd) - Doozer is a highly-available, completely consistent store for small amounts of extremely important data.
⟡ etcd (https://github.com/coreos/etcd) - A highly-available key value store for shared configuration and service discovery.
⟡ Juju (https://juju.ubuntu.com/) - Cloud orchestration tool which manages services as charms, YAML configuration and deployment script bundles.
⟡ MCollective (http://puppetlabs.com/mcollective) - Ruby framework to manage server orchestration, developed by Puppet labs.
⟡ Overcast (http://andrewchilds.github.io/overcast/) - Deploy VMs across different cloud providers, and run commands and scripts across any or all of them in parallel via SSH.
⟡ Rundeck (http://rundeck.org/) - Simple orchestration tool.
⟡ Salt (http://www.saltstack.com/) - Fast, scalable and flexible systems management software written in Python/ZeroMQ.
⟡ serf (http://www.serfdom.io/) - Serf is a tool for cluster membership.
⟡ StackStorm (http://stackstorm.com/) - Event Driven Operations and ChatOps platform for infrastructure management. Written in Python.
⟡ zookeeper (http://zookeeper.apache.org/) - ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.

Cloud Storage

⟡ git-annex assistant (http://git-annex.branchable.com/assistant/) - A synchronised folder on each of your OSX and Linux computers, Android devices, removable drives, NAS appliances, and cloud services.
⟡ nextCloud (https://nextcloud.com) - Provides access to your files via the web
⟡ ownCloud (https://owncloud.org) - Provides universal access to your files via the web, your computer or your mobile devices.
⟡ Seafile (http://seafile.com) - Another Open Source Cloud Storage solution.
⟡ SparkleShare (http://sparkleshare.org/) - Provides cloud storage and file synchronization services. By default, it uses Git as a storage backend.
⟡ Swift (http://docs.openstack.org/developer/swift/) - A highly available, distributed, eventually consistent object/blob store.
⟡ Syncthing (http://syncthing.net/) - Open Source system for private, encrypted and authenticated distribution of data.

Code Review

Web Based collaborative code review system.

⟡ Gerrit (https://code.google.com/p/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 (http://phabricator.org/) - 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 (https://www.reviewboard.org/) - Web-based collaborative code review tool.

Collaborative Software

Collaborative software or groupware suites.

⟡ Citadel/UX (http://www.citadel.org/) - Collaboration suite (messaging and groupware) that is descended from the Citadel family of programs.
⟡ EGroupware (http://www.egroupware.org/) - Groupware software written in PHP.
⟡ Horde Groupware (http://www.horde.org/apps/groupware) - PHP based collaborative software suite that includes email, calendars, wikis, time tracking and file management.
⟡ Kolab (https://www.kolab.org) - Another groupware suite.
⟡ SOGo (https://www.sogo.nu/) - Collaborative software server with a focus on simplicity and scalability.
⟡ Zimbra (https://www.zimbra.com/community/) - Collaborative software suite, that includes an email server and web client.

Configuration Management Database

Configuration management database (CMDB) software.

⟡ Clusto (https://github.com/clusto/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 (http://tumblr.github.io/collins) - At Tumblr, it's the infrastructure source of truth and knowledge.
⟡ i-doit (http://www.i-doit.org/) - Open Source IT Documentation and CMDB.
⟡ iTop (http://www.combodo.com/-Overview-.html) - Complete open source, ITIL, web based service management tool.
⟡ Ralph (https://github.com/allegro/ralph) - Asset management, DCIM and CMDB system for large Data Centers as well as smaller LAN networks.
⟡ Sicekit (https://github.com/sicekit/sicekit) - The systems & infrastructure encyclopaedia toolkit (based on MediaWiki).

Configuration Management

Configuration management tools.

⟡ Ansible (http://www.ansible.com/) -  It's written in Python and manages the nodes over SSH.
⟡ CFEngine (http://cfengine.com/) - Lightweight agent system. Configuration state is specified via a declarative language.
⟡ Chef (http://www.opscode.com/chef/) - It's written in Ruby and Erlang and uses a pure-Ruby DSL.
⟡ mgmt (https://github.com/purpleidea/mgmt) - Next generation config management written in Go.
⟡ Pallet (http://palletops.com/) - Infrastructure definition, configuration and management via a Clojure DSL.
⟡ Puppet (http://puppetlabs.com/) - It's written in Ruby and uses Puppet's declarative language or a Ruby DSL.
⟡ (R)?ex (https://www.rexify.org/) - It's written in Perl and use plain Perl, over SSH without agent.
⟡ Salt (http://www.saltstack.com/) - It's written in Python.
⟡ Slaughter (http://steve.org.uk/Software/slaughter/) - It's written in Perl.

Continuous Integration & Continuous Deployment

Continuous integration/deployment software.

⟡ Buildbot (http://buildbot.net/) - Python-based toolkit for continuous integration.
⟡ Drone (https://github.com/drone/drone) - Continuous integration server built on Docker and configured using YAML files.
⟡ GitLab CI (https://www.gitlab.com/gitlab-ci/) - Based off of ruby. They also provide GitLab, which manages git repositories.
⟡ Go (http://www.go.cd/) - Open source continuous delivery server.
⟡ Jenkins (http://jenkins-ci.org/) - An extendable open source continuous integration server.
⟡ Concourse CI (https://concourse.ci/) - A pipeline-based CI system written in Go.
⟡ Spinnaker (http://www.spinnaker.io/) - Open source, multi-cloud continuous delivery platform for releasing software changes.
⟡ TeamCity (https://www.jetbrains.com/teamcity/) - Powerful Continuous Integration out of the box

Control Panels

Web hosting and server control panels.

⟡ Ajenti (http://ajenti.org/) - Control panel for Linux and BSD.
⟡ Cockpit (http://cockpit-project.org/) - New multi-server web interface for Linux servers written in C.
⟡ Feathur (http://feathur.com) - VPS Provisioning and Management Software.
⟡ Froxlor (http://www.froxlor.org/) - Easy to use panel for Linux with Nginx and PHP-FPM support.
⟡ ISPConfig (http://www.ispconfig.org) - Hosting control panel for Linux.
⟡ Sentora (http://sentora.org/) - Control panel for Linux, BSD, and Windows based on ZPanel.
⟡ VestaCP (http://www.vestacp.com/) - Hosting panel for Linux but with Nginx.
⟡ Virtualmin (http://www.virtualmin.com/) - Control panel for Linux based on webmin.
⟡ Webmin (http://www.webmin.com/) - Linux server control panel.
⟡ ZPanel (http://www.zpanelcp.com/) - Control panel for Linux, BSD, and Windows.

Deployment Automation

Tools and scripts to support deployments to your servers.

⟡ Capistrano (http://www.capistranorb.com) - Deploy your application to any number of machines simultaneously, in sequence or as a rolling set via SSH (rake based).
⟡ Fabric (http://www.fabfile.org/) - Python library and cli tool for streamlining the use of SSH for application deployment or systems administration tasks.
⟡ Mina (http://nadarei.co/mina/) - Really fast deployer and server automation tool (rake based).
⟡ Rocketeer (http://rocketeer.autopergamene.eu/) - PHP task runner and deployment tool.
⟡ Vlad the Deployer (http://rubyhitsquad.com/Vlad_the_Deployer.html) - Deployment automation (rake based).

Diagramming

Tools to diagram networks.

⟡ drawthe.net (http://go.drawthe.net/) - Draws network diagrams dynamically from a text file describing the placement, layout and icons.

Distributed Filesystems

Network distributed filesystems.

⟡ Ceph (http://ceph.com/) - Distributed object store and file system.
⟡ DRBD (http://www.drbd.org/) - Distributed Replicated Block Device.
⟡ LeoFS (http://leo-project.net) - Unstructured object/data storage and a highly available, distributed, eventually consistent storage system.
⟡ GlusterFS (http://www.gluster.org/) - Scale-out network-attached storage file system.
⟡ HDFS (http://hadoop.apache.org/) - Distributed, scalable, and portable file-system written in Java for the Hadoop framework.
⟡ Lustre (http://lustre.opensfs.org/) -  A type of parallel distributed file system, generally used for large-scale cluster computing.
⟡ MooseFS (http://www.moosefs.org/) - Fault tolerant, network distributed file system.
⟡ MogileFS (http://mogilefs.org/) - Application level, network distributed file system.
⟡ OpenAFS (http://www.openafs.org/) - Distributed network file system with read-only replicas and multi-OS support.
⟡ TahoeLAFS (https://tahoe-lafs.org/trac/tahoe-lafs) - secure, decentralized, fault-tolerant, peer-to-peer distributed data store and distributed file system.
⟡ XtreemFS (http://www.xtreemfs.org/) - XtreemFS is a fault-tolerant distributed file system for all storage needs.

DNS

DNS servers.

⟡ Bind (https://www.isc.org/downloads/bind/) - The most widely used name server software.
⟡ djbdns (http://cr.yp.to/djbdns.html) - A collection of DNS applications, including tinydns.
⟡ Designate (https://wiki.openstack.org/wiki/Designate) - DNS REST API that support several DNS servers as its backend.
⟡ dnsmasq (http://www.thekelleys.org.uk/dnsmasq/doc.html) - A lightweight service providing DNS, DHCP and TFTP services to small-scale networks.
⟡ Knot (https://www.knot-dns.cz/) - High performance authoritative-only DNS server.
⟡ NSD (http://www.nlnetlabs.nl/projects/nsd/) - Authoritative only, high performance, simple name server.
⟡ PowerDNS (https://www.powerdns.com/) - DNS server with a variety of data storage back-ends and load balancing features.
⟡ Unbound (http://unbound.net/) - Validating, recursive, and caching DNS resolver.
⟡ Yadifa (http://yadifa.eu/) - Lightweight authoritative Name Server with DNSSEC capabilities powering the .eu top-level domain.

Editors

Open source code editors.

⟡ Atom (https://atom.io/) - A hackable text editor from GitHub.
⟡ Brackets (http://brackets.io/) - Open source code editor for web designers and front-end developers.
⟡ Eclipse (http://eclipse.org/) - IDE written in Java with an extensible plug-in system.
⟡ Geany (http://www.geany.org/) - GTK2 text editor.
⟡ GNU Emacs (http://www.gnu.org/software/emacs/) - An extensible, customizable text editor-and more.
⟡ Haroopad (http://pad.haroopress.com/) - Markdown editor with live preview.
⟡ ICEcoder (http://icecoder.net) - Code editor awesomeness, built with common web languages.
⟡ IntellijIDEA (https://github.com/JetBrains/intellij-community) - Capable and ergonomic IDE, written in Java, It has a lot of plug-ins.
⟡ jotgit (https://github.com/jdleesmiller/jotgit) - Git-backed real-time collaborative code editing.
⟡ Light Table (http://www.lighttable.com/) - The next generation code editor.
⟡ Lime (http://limetext.org/) - Aims to provide an open source solution to Sublime Text
⟡ SciTE (http://www.scintilla.org/SciTE.html) - A SCIntilla based Text Editor.
⟡ TextMate (https://github.com/textmate/textmate/) - A graphical text editor for OS X.
⟡ Vim (http://www.vim.org) - A highly configurable text editor built to enable efficient editing.
⟡ Nano (http://https://www.nano-editor.org/) - A popular text editor, by default comes with most Linux distributions.
⟡ Visual Studio Code (https://code.visualstudio.com/) - Fast, hackable, multi-platform code editor from Microsoft.

IT Asset Management

IT Assets Management software.

⟡ GLPI (http://www.glpi-project.org/spip.php?lang=en) - Information Resource-Manager with an additional Administration Interface.
⟡ OCS Inventory NG (http://www.ocsinventory-ng.org/en/) - Enables users to inventory their IT assets.
⟡ Netbox (https://github.com/digitalocean/netbox) - IP address management (IPAM) and data center infrastructure management (DCIM) tool.
⟡ RackTables (http://racktables.org/) - Datacenter and server room asset management like document hardware assets, network addresses, space in racks, networks configuration.
⟡ Ralph (https://github.com/allegro/ralph) - Asset management, DCIM and CMDB system for large Data Centers as well as smaller LAN networks.
⟡ Snipe IT (http://snipeitapp.com/) - Asset & license management software.
⟡ OpenDCIM (http://www.opendcim.org/) - A web based Data Center Infrastructure Management application.

LDAP

LDAP servers.

⟡ 389 Directory Server (http://port389.org) - Developed by Red Hat.
⟡ Apache Directory Server (http://directory.apache.org/) - Apache Software Foundation project written in Java.
⟡ Fusion Directory (http://www.fusiondirectory.org) - Improve the Management of the services and the company directory based on OpenLDAP.
⟡ OpenDJ (http://opendj.forgerock.org/) - Fork of OpenDS.
⟡ OpenDS (https://opends.java.net/) - Another directory server written in Java.
⟡ OpenLDAP (http://openldap.org/) - Developed by the OpenLDAP Project.

LDAP management

⟡ Apache Directory Studio (https://directory.apache.org/studio/) - The Eclipse-based LDAP browser and directory client

Log Management

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

⟡ Echofish (http://www.echothrust.com/projects/echofish) - A web based real-time event log aggregation, analysis, monitoring and management system.
⟡ Elasticsearch (http://www.elasticsearch.org/) - A Lucene Based Document store mainly used for log indexing, storage and analysis.
⟡ Fluentd (http://www.fluentd.org/) - Log Collector and Shipper.
⟡ Flume (https://flume.apache.org/) - Distributed log collection and aggregation system.
⟡ Graylog2 (http://graylog2.org/) - Pluggable Log and Event Analysis Server with Alerting options.
⟡ Heka (http://hekad.readthedocs.org/en/latest/) - Stream processing system which may be used for log aggregation.
⟡ Kibana (http://www.elasticsearch.org/overview/kibana/) - Visualize logs and time-stamped data.
⟡ Logstash (http://logstash.net/) - Tool for managing events and logs.
⟡ Octopussy (http://www.octopussy.pm) - Log Management Solution (Visualize / Alert / Report).

Mail Servers

Mail Delivery Agents (IMAP/POP3 software).

⟡ Courier IMAP/POP3 (http://www.courier-mta.org/imap/) - Fast, scalable, enterprise IMAP and POP3 server.
⟡ Cyrus IMAP/POP3 (http://cyrusimap.org/) - Intended to be run on sealed servers, where normal users are not permitted to log in.
⟡ Dovecot (http://www.dovecot.org/) - IMAP and POP3 server written primarily with security in mind.
⟡ Qpopper (http://www.eudora.com/products/unsupported/qpopper/) - One of the oldest and most popular server implementations of POP3.

Mail Transfer Agents (SMTP servers).

⟡ Exim (http://www.exim.org/) - Message transfer agent (MTA) developed at the University of Cambridge.
⟡ Haraka (http://haraka.github.io/) - A high-performance, pluginable SMTP server written in JavaScript.
⟡ MailCatcher (http://mailcatcher.me/) - Ruby gem that deploys a simply SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development.
⟡ Maildrop (https://github.com/m242/maildrop) - Open Source disposable email SMTP server, also useful for development.
⟡ OpenSMTPD (https://opensmtpd.org/) - Secure SMTP server implementation from the OpenBSD project.
⟡ Postfix (http://www.postfix.org/) - Fast, easy to administer, and secure Sendmail replacement.
⟡ Qmail (http://cr.yp.to/qmail.html) - Secure Sendmail replacement.
⟡ Sendmail (http://www.sendmail.com/sm/open_source/) - Message transfer agent (MTA).

Complete solutions.

⟡ Mail-in-a-Box (https://mailinabox.email/) - Take back control of your email with this easy-to-deploy mail server in a box.
⟡ iRedMail (http://www.iredmail.org/) - Full-featured mail server solution based on Postfix and Dovecot.

Messaging

XMPP servers.

⟡ ejabberd (http://www.ejabberd.im/) - XMPP instant messaging server written in Erlang/OTP.
⟡ Metronome IM (http://www.lightwitch.org/metronome) - Fork of Prosody IM.
⟡ MongooseIM (https://www.erlang-solutions.com/products/mongooseim.html) - Fullstack real-time mobile messaging platform (XMPP+REST) in Erlang
⟡ Openfire (http://www.igniterealtime.org/projects/openfire/) - Real time collaboration (RTC) server.
⟡ Prosody IM (http://prosody.im/) - XMPP server written in Lua.
⟡ Tigase (https://projects.tigase.org/projects/tigase-server) - XMPP server implementation in Java.

XMPP web clients.

⟡ Candy (http://candy-chat.github.io/candy/) - Multi user XMPP client written in Javascript.
⟡ Kaiwa (http://getkaiwa.com/) - Web based chat client in the style of common paid alternatives.

Webchats.

⟡ Lets-Chat (http://sdelements.github.io/lets-chat/) - A self hosted chat suite written in Node.

Monitoring

Monitoring software.

⟡ Alerta (https://github.com/guardian/alerta) - Distributed, scaleable and flexible monitoring system.
⟡ Canopsis (http://www.canopsis.org) - Opensource Hypervision and Data Aggregation Software
⟡ Cacti (http://www.cacti.net) - Web-based network monitoring and graphing tool.
⟡ Cabot (http://cabotapp.com/) - Monitoring and alerts, similar to PagerDuty.
⟡ Centreon (http://www.centreon.com) - IT infrastructure and application monitoring for service performance.
⟡ check_mk (http://mathias-kettner.com/check_mk.html) - Collection of extensions for Nagios.
⟡ Flapjack (http://flapjack.io/) - Monitoring notification routing & event processing system.
⟡ Icinga (https://www.icinga.org/) - Fork of Nagios.
⟡ LibreNMS (https://github.com/librenms/librenms/) - fork of Observium.
⟡ Monit (http://mmonit.com/monit/#home) - Small Open Source utility for managing and monitoring Unix systems.
⟡ Munin (http://munin-monitoring.org/) - Networked resource monitoring tool.
⟡ Naemon (http://www.naemon.org/) - Network monitoring tool based on the Nagios 4 core with performance enhancements and new features.
⟡ Nagios (http://www.nagios.org/) - Computer system, network and infrastructure monitoring software application.
⟡ Node-Bell (https://github.com/eleme/node-bell) - Real-time anomalies detection for periodic time series, metrics monitor.
⟡ Observium (http://www.observium.org/) - SNMP monitoring for servers and networking devices. Runs on linux.
⟡ Opsview (http://www.opsview.com/solutions/core) - Based on Nagios 4, Opsview Core is ideal for small IT and test environments.
⟡ Riemann (http://riemann.io/) - Flexible and fast events processor allowing complex events/metrics analysis.
⟡ Sensu (http://sensuapp.org/) - Open source monitoring framework.
⟡ Sentry (https://getsentry.com/) - Application monitoring, event logging and aggregation.
⟡ Serverstats (https://sourceforge.net/projects/serverstats.berlios/) - A simple tool for creating graphs using rrdtool. (source on github (https://github.com/ddanier/serverstats))
⟡ Seyren (https://github.com/scobal/seyren) - An alerting dashboard for Graphite.
⟡ Shinken (http://www.shinken-monitoring.org/) - Another monitoring framework.
⟡ Xymon (http://www.xymon.com/) - Network monitoring inspired by Big Brother.
⟡ Zabbix (http://www.zabbix.com/) - Enterprise-class software for monitoring of networks and applications.
⟡ Zenoss (http://community.zenoss.org) - Application, server, and network management platform based on Zope.

Monitoring dashboards.

⟡ Adagios (http://adagios.org/) - Web based Nagios configuration interface.
⟡ Dash (https://github.com/afaqurk/linux-dash) - A low-overhead monitoring web dashboard for a GNU/Linux machine.
⟡ Thruk (http://www.thruk.org/) - Multibackend monitoring web interface with support for Naemon, Nagios, Icinga and Shinken.
⟡ Uchiwa (https://uchiwa.io) - Simple dashboard for the Sensu monitoring framework.

Monitoring distributions.

⟡ OMD (http://omdistro.org/) - The Open Monitoring Distribution.

Metric & Metric Collection

Metric gathering and display software.

⟡ Collectd (http://collectd.org/) - System statistic collection daemon.
⟡ Collectl (http://collectl.sourceforge.net/) - High precision system performance metrics collecting tool.
⟡ dashing (http://dashing.io/) - __No Longer Maintained__ - Ruby gem that allows for rapid statistical dashboard development. An all HTML5 approach allows for big screen displays in data centers or conference rooms.
⟡ Smashing (https://github.com/Smashing/smashing) - Ruby gem that allows for rapid statistical dashboard development. An all HTML5 approach allows for big screen displays in data centers or conference rooms. Fork of Dashing.
⟡ Diamond (https://github.com/BrightcoveOS/Diamond) - Python based statistic collection daemon.
⟡ Facette (http://facette.io) - Time series data visualization and graphing software written in Go.
⟡ Freeboard (https://github.com/Freeboard/freeboard) - A damn-sexy front-end real-time dashboard. Transforms raw JSON into delicious UI.
⟡ Ganglia (http://ganglia.sourceforge.net/) - High performance, scalable RRD based monitoring for grids and/or clusters of servers. Compatible with Graphite using a single collection process.
⟡ Grafana (http://grafana.org/) - A Graphite & InfluxDB Dashboard and Graph Editor.
⟡ Graphite (http://graphite.readthedocs.org/en/latest/) - Open source scalable graphing server.
⟡ InfluxDB (http://influxdb.com/) - Open source distributed time series database with no external dependencies.
⟡ KairosDB (https://code.google.com/p/kairosdb/) - Fast distributed scalable time series database, fork of OpenTSDB 1.x.
⟡ NetData (http://my-netdata.io) - Distributed real-time performance and health monitoring.
⟡ OpenTSDB (http://opentsdb.net/) - Store and server massive amounts of time series data without losing granularity.
⟡ Packetbeat (http://packetbeat.com/) - Captures network traffic and displays it in a custom Kibana dashboard for easy viewing.
⟡ Prometheus (http://prometheus.io/) - Service monitoring system and time series database.
⟡ RRDtool (http://oss.oetiker.ch/rrdtool/) - Open source industry standard, high performance data logging and graphing system for time series data.
⟡ Statsd (https://github.com/etsy/statsd/) - Application statistic listener.

Network Configuration Management

Network configuration management tools.

⟡ GestióIP (http://www.gestioip.net/) - An automated web based IPv4/IPv6 IP Address Management tool.
⟡ NOC Project (http://nocproject.org/) - Scalable, high-performance and open-source OSS (http://en.wikipedia.org/wiki/Operations_support_system) system for ISP, service and content providers.
⟡ Netbox (https://github.com/digitalocean/netbox) - IP address management (IPAM) and data center infrastructure management (DCIM) tool.
⟡ Oxidized (https://github.com/ytti/oxidized) - A modern take on network device configuration monitoring with web interface and GIT storage.
⟡ phpIPAM (http://phpipam.net/) - Open source IP address management with PowerDNS (https://www.powerdns.com/) integration.
⟡ RANCID (http://www.shrubbery.net/rancid/) - Monitors network device's configuration and maintain history of changes.
⟡ rConfig (http://www.rconfig.com/) - Another network device configuration management tool.
⟡ trigger (https://github.com/trigger/trigger) - Robust network automation toolkit written in Python.


Newsletters

Newsletter software.

⟡ DadaMail (http://dadamailproject.com/) - Mailing List Manager, written in Perl.
⟡ phpList (http://www.phplist.com/) - Newsletter manager written in PHP.

NoSQL

Column-Family.

  ⟡ Apache HBase (http://hbase.apache.org/) - Hadoop database, a distributed, big data store.
  ⟡ Cassandra (http://cassandra.apache.org/) - Distributed DBMS designed to handle large amounts of data across many servers.
  ⟡ Hypertable (http://hypertable.org/) - C++ based BigTable-like DBMS, communicates through Thrift and runs either as stand-alone or on distributed FS such as Hadoop.

Document Store.

  ⟡ CouchDB (http://couchdb.apache.org/) - Ease of use, with multi-master replication document-oriented database system.
  ⟡ ElasticSearch (http://www.elasticsearch.org/) - Java based database, popular with log aggregation, and email archiving projects.
  ⟡ MongoDB (http://www.mongodb.org/) - Another document-oriented database system.
  ⟡ RavenDB (http://ravendb.net/) - Document based database with ACID/Transactional features.
  ⟡ RethinkDB (http://www.rethinkdb.com/) - Open source distributed document store database, focuses on JSON.

Graph.

  ⟡ FlockDB (https://github.com/twitter/flockdb) - Twitter's distributed, fault-tolerant graph database.
  ⟡ Neo4j (http://www.neo4j.org/) - Open source graph database.

Key-Value.

  ⟡ Couchbase (http://www.couchbase.com/) - In-memory, replicated, peristent key/value datastore.
  ⟡ LevelDB (https://github.com/google/leveldb) - Google's high performance key/value database.
  ⟡ Redis (http://redis.io/) - Networked, in-memory, key-value data store with optional durability.
  ⟡ Riak (http://basho.com/riak/) - Another fault-tolerant key-value NoSQL database.

Packaging

⟡ fpm (https://github.com/jordansissel/fpm) - Versatile multi format package creator.
⟡ omnibus-ruby (https://github.com/opscode/omnibus-ruby) - Full stack, cross distro packaging software (Ruby).
⟡ packman (http://packman.readthedocs.org) - Full stack, cross distro packaging software (Python).
⟡ tito (https://github.com/dgoodwin/tito) - Builds RPMs for git-based projects.

Queuing

Queuing software.

⟡ ActiveMQ (http://activemq.apache.org/) - An open source message broker written in Java together with a full JMS client.
⟡ BeanstalkD (http://kr.github.io/beanstalkd/) - A simple, fast work queue.
⟡ Gearman (http://gearman.org/) - Fast multi-language queuing/job processing platform.
⟡ Kafka (http://kafka.apache.org/) - A high-throughput distributed messaging system.
⟡ NSQ (http://nsq.io/) - A realtime distributed messaging platform.
⟡ RabbitMQ (http://www.rabbitmq.com/) - Robust, fully featured, cross distro queuing system.

Queuing libraries.

⟡ ZeroMQ (http://zeromq.org/) -  High-performance asynchronous messaging library.

RDBMS
Relational DBMS.

⟡ Firebird (http://www.firebirdsql.org/) - True universal open source database.
⟡ Galera (http://galeracluster.com/) - 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 (https://mariadb.org/) - Community-developed fork of the MySQL.
⟡ MySQL (http://dev.mysql.com/) - Most popular RDBMS server.
⟡ Percona Server (http://www.percona.com/software) - Enhanced, drop-in MySQL replacement.
⟡ PostgreSQL (http://www.postgresql.org/) - Object-relational database management system (ORDBMS).
⟡ PostgreSQL-XL (http://www.postgres-xl.org/) - Scalable Open Source PostgreSQL-based database cluster.
⟡ SQLite (http://sqlite.org/) - Library that implements a self-contained, serverless, zero-configuration, transactional SQL DBS.

Security

Security tools.

⟡ Blackbox (https://github.com/StackExchange/blackbox) - Safely store secrets in Git/Mercurial. Provides tooling to automatically encrypt secrets like passwords.
⟡ Denyhosts (http://denyhosts.sourceforge.net/) - Thwart SSH dictionary based attacks and brute force attacks.
⟡ Fail2Ban (http://www.fail2ban.org/wiki/index.php/Main_Page) - Scans log files and takes action on IPs that show malicious behavior.
⟡ fwknop (https://www.cipherdyne.org/fwknop/) - Protects ports via Single Packet Authorization in your firewall.
⟡ Glastopf (http://glastopf.org/) - A low-interaction web application honeypot to emulate vulnerabilities and gather attack data.
⟡ Kippo (https://github.com/desaster/kippo) - A medium-interaction SSH honeypot, mostly used as a standalone SSH daemon with a configurable Filesystem sandbox.
⟡ OSSEC (http://ossec.net) - OSSEC is a HIDS that performs log analysis, FIM, rootkit detection, and much more.
⟡ OSQuery (https://osquery.io/) - Query your servers status and info using a SQL like interface.
⟡ pfSense (https://www.pfsense.org/) - Firewall and Router FreeBSD distribution.
⟡ Snort (https://www.snort.org/) - 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 (https://spamassassin.apache.org/) - A powerful and popular email spam filter employing a variety of detection technique.
⟡ BounCA (https://bounca.org/) - BounCA is a personal SSL / Certificate Authority Key management tool. Create self-signed SSL certificates via your browser. (Source Code (https://github.com/repleo/bounca)) Apache Python

Service Discovery

⟡ Consul (http://www.consul.io/) - Consul is a tool for service discovery, monitoring and configuration.
⟡ Doozerd (https://github.com/ha/doozerd) - Doozer is a highly-available, completely consistent store for small amounts of extremely important data.
⟡ ZooKeeper (http://zookeeper.apache.org/) - ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services.

Software Containers

Operating system–level virtualization.

⟡ Bitnami (https://bitnami.com/) - Produces open source installers or software packages for web applications and development stacks as well as virtual appliances.
⟡ Docker (http://www.docker.com/) - Open platform for developers and sysadmins to build, ship, and run distributed applications.
⟡ LXC (https://linuxcontainers.org/lxc/) -  Userspace interface for the Linux kernel containment features.
⟡ LXD (https://linuxcontainers.org/lxd/) - LXD is a container "hypervisor".
⟡ OpenVZ (http://openvz.org) - Container-based virtualization for Linux.
⟡ Docker Compose (https://docs.docker.com/compose/) - Fast, isolated development environments using Docker.
⟡ Singularity (http://singularity.lbl.gov/) - Flexible containers without root.

SSH

SSH tools.

⟡ Advanced SSH config (https://pypi.python.org/pypi/advanced-ssh-config/) - Enhances ssh_config file capabilities, completely transparent.
⟡ autossh (http://www.harding.motd.ca/autossh/) - Automatically respawn ssh session after network interruption.
⟡ Cluster SSH (http://sourceforge.net/projects/clusterssh/) - Controls a number of xterm windows via a single graphical console.
⟡ DSH (http://www.netfort.gr.jp/~dancer/software/dsh.html.en) - Dancer's shell / distributed shell - Wrapper for executing multiple remote shell commands from one command line.
⟡ Mosh (http://mosh.mit.edu/) - The mobile shell.
⟡ parallel-ssh (http://code.google.com/p/parallel-ssh/) - Provides parallel versions of OpenSSH and related tools.
⟡ pdsh (https://code.google.com/p/pdsh/) - Pdsh is a high-performance, parallel remote shell utility.
⟡ SSH Power Tool (http://code.google.com/p/sshpt/) - Execute commands and upload files to many servers simultaneously without using pre-shared keys.
⟡ sshrc (https://github.com/Russell91/sshrc) - sources ~/.sshrc on your local computer after logging in remotely.
⟡ stormssh (http://stormssh.readthedocs.org) - A command line tool to manage SSH connections.

Statistics

Analytics software.

⟡ Analog (http://www.web42.com/analog/) - Logfile Analyser.
⟡ AWStats (http://www.awstats.org/) - Generates web, streaming, ftp or mail server statistics graphically.
⟡ GoAccess (http://goaccess.io/) - Real-time web log analyzer and interactive viewer that runs in a terminal.
⟡ Open Web Analytics (http://www.openwebanalytics.com/) - Add web analytics to websites using JS, PHP or REST APIs.
⟡ Piwik (http://piwik.org/) - Web analytics application.
⟡ Webalizer (http://www.webalizer.org/) - Fast, free web server log file analysis program.

Status Pages

⟡ Cachet (https://cachethq.io) - An open source status page system written in PHP.

Ticketing systems

Web-based ticketing system.

⟡ Bugzilla (http://www.bugzilla.org/) - General-purpose bugtracker and testing tool originally developed and used by the Mozilla project.
⟡ Cerb (http://www.cerberusweb.com/) - Group-based e-mail management project.
⟡ Flyspray (http://flyspray.org) - Web-based bug tracking system written in PHP.
⟡ MantisBT (http://www.mantisbt.org/) - Web-based bug tracking system.
⟡ osTicket (http://osticket.com/) - Simple support ticket system.
⟡ OTRS (http://www.otrs.com/) - Trouble ticket system for assigning tickets to incoming queries and tracking further communications.
⟡ Redmine (http://www.redmine.org/) - Open source project management/ticketing web application written in Ruby.
⟡ Request Tracker (http://www.bestpractical.com/rt/) - Ticket-tracking system written in Perl.
⟡ TheBugGenie (http://www.thebuggenie.com) - Ticket system with extensive user rights system.

Troubleshooting

Troubleshooting tools.

⟡ mitmproxy (http://mitmproxy.org/) - A Python tool used for intercepting, viewing and modifying network traffic. Invaluable in troubleshooting certain problems.
⟡ Sysdig (http://www.sysdig.org/) - Capture system state and activity from a running Linux instance, then save, filter and analyze.
⟡ Wireshark (http://www.wireshark.org/) - The world's foremost network protocol analyzer.

Troubleshooting distributions.

⟡ Trinity Rescue Kit (http://trinityhome.org) - Linux Live CD for general computer troubleshooting.

Project Management

Web-based project management and bug tracking systems.

⟡ ChiliProject (https://www.chiliproject.org) - Fork of Redmine.
⟡ GitBucket (https://github.com/takezoe/gitbucket) Clone of GitHub written in Scala; single jar install.
⟡ GitLab (https://www.gitlab.com/) - Clone of GitHub written in Ruby.
⟡ Gogs (http://gogs.io/) - Self-hosted Git service written in Go.
⟡ OpenProject (https://www.openproject.org) - Project collaboration with open source.
⟡ Phabricator (http://phabricator.org/) Written in PHP.
⟡ Redmine (http://www.redmine.org/) - Written in ruby on rails.
⟡ Taiga (https://taiga.io/) - Agile, Free, Open Source Project Management Tool based on the Kanban and Scrum methods.
⟡ The Bug Genie (http://www.thebuggenie.com/) - Written in PHP.
⟡ Trac (http://trac.edgewall.org/) - Written in python.

Version control

Software versioning and revision control.

⟡ Fossil (http://www.fossil-scm.org/) - Distributed version control with built-in wiki and bug tracking.
⟡ Git (http://git-scm.com/) - Distributed revision control and source code management (SCM) with an emphasis on speed.
⟡ GNU Bazaar (http://bazaar.canonical.com/) - Distributed revision control system sponsored by Canonical.
⟡ Mercurial (http://mercurial.selenic.com/) - Another distributed revision control.
⟡ Subversion (http://subversion.apache.org/) - Client-server revision control system.

Virtualization

Virtualization software.

⟡ Archipel (http://archipelproject.org/) - XMPP based virtualization management platform.
⟡ Ganeti (https://code.google.com/p/ganeti/) - Cluster virtual server management software tool built on top of KVM and Xen.
⟡ KVM (http://www.linux-kvm.org) - Linux kernel virtualization infrastructure.
⟡ OpenNebula (http://opennebula.org/) - Flexible enterprise cloud made simple.
⟡ oVirt (http://www.ovirt.org/) - Manages virtual machines, storage and virtual networks.
⟡ Packer (http://www.packer.io/) - A tool for creating identical machine images for multiple platforms from a single source configuration.
⟡ Proxmox VE (https://www.proxmox.com/proxmox-ve) - Complete open source virtualization management solution.
⟡ QEMU (http://www.qemu.org/) - QEMU is a generic and open source machine emulator and virtualizer.
⟡ Vagrant (https://www.vagrantup.com/) - Tool for building complete development environments.
⟡ VirtualBox (https://www.virtualbox.org/) - Virtualization product from Oracle Corporation.
⟡ Xen (http://www.xenproject.org/) - Virtual machine monitor for 32/64 bit Intel / AMD (IA 64) and PowerPC 970 architectures.

VPN

VPN software.

⟡ OpenVPN (https://community.openvpn.net) - Uses a custom security protocol that utilizes SSL/TLS for key exchange.
⟡ Pritunl (http://pritunl.com/) - OpenVPN based solution. Easy to set up.
⟡ SoftEther (https://www.softether.org/) - Multi-protocol software VPN with advanced features
⟡ sshuttle (https://github.com/apenwarr/sshuttle) - Poor man's VPN.
⟡ strongSwan (http://www.strongswan.org/) - Complete IPsec implementation for Linux.
⟡ tinc (http://www.tinc-vpn.org/) - Distributed p2p VPN.
⟡ wireguard (https://www.wireguard.com/) - New minimal VPN Solution that is very fast.

Web

Web servers.

⟡ Apache (http://httpd.apache.org/) - Most popular web server.
⟡ Caddy (https://caddyserver.com/) - The HTTP/2 Web Server with Fully Managed TLS.
⟡ Cherokee (http://cherokee-project.com/) - Lightweight, high-performance web server/reverse proxy.
⟡ Lighttpd (http://www.lighttpd.net/) - Web server more optimized for speed-critical environments.
⟡ Nginx (http://nginx.org/) - Reverse proxy, load balancer, HTTP cache, and web server.
⟡ uWSGI (https://github.com/unbit/uwsgi/) - The uWSGI project aims at developing a full stack for building hosting services.

Web Performance.

⟡ HAProxy (http://www.haproxy.org/) - Software based load Balancing, SSL offloading and performance optimization, compression, and general web routing.
⟡ Squid (http://www.squid-cache.org/) - Caching proxy for the web supporting HTTP, HTTPS, FTP, and more.
⟡ Traefik (https://traefik.io/) - Træfɪk is a modern HTTP reverse proxy and load balancer made to deploy microservices with ease.
⟡ Varnish (https://www.varnish-cache.org/) - HTTP based web application accelerator focusing on optimizing caching and compression.

Webmails

Webmail applications.

⟡ Mailpile (https://www.mailpile.is/) - A modern, fast web-mail client with user-friendly encryption and privacy features.
⟡ Roundcube (http://roundcube.net/) - Browser-based IMAP client with an application-like user interface.
⟡ SquirrelMail (http://squirrelmail.org) - Another browser-based IMAP client.

Wikis

Wiki software.

⟡ BookStack (https://www.bookstackapp.com/) - A simple, user-friendly wiki built with PHP that uses MySQL for storage.
⟡ DokuWiki (https://www.dokuwiki.org/dokuwiki) - Simple to use and highly versatile wiki that doesn't require a database.
⟡ Gollum (https://github.com/gollum/gollum) - A simple, Git-powered wiki with a sweet API and local frontend.
⟡ ikiwiki (http://ikiwiki.info/) - A wiki compiler.
⟡ MDwiki (http://dynalon.github.io/mdwiki/#!index.md) - Wiki completely built in HTML5/Javascript and runs 100% on the client.
⟡ MediaWiki (http://www.mediawiki.org/wiki/MediaWiki) - Used to power Wikipedia.
⟡ MoinMoin (http://moinmo.in/) - An advanced, easy to use and extensible WikiEngine with a large community of users.
⟡ Ōlelo Wiki (https://github.com/minad/olelo) - A a wiki that stores pages in a Git repository.
⟡ TiddlyWiki (http://tiddlywiki.com) - Complete interactive wiki in JavaScript.

                                                                                                                 Resources

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

Blogs

⟡ Code as Craft (http://codeascraft.com/) - Etsy's Ops blog, lots of technical posts.
⟡ DevOpsGuys (http://blog.devopsguys.com/) - Devops consultants who blog about operations.
⟡ Rackspace Developers (http://developer.rackspace.com/blog/) - Slightly biased blog with lots of Devops Topics.

Books

Sysadmin related books.

⟡ Learn Cisco Network Administration in a Month of Lunches
  (https://www.manning.com/books/learn-cisco-network-administration-in-a-month-of-lunches) - A tutorial designed for sysadmins who need to learn how to administer Cisco switches and routers.
⟡ The Linux Command Line (http://linuxcommand.org/tlcl.php) - A book about the Linux command line by William Shotts.
⟡ The Phoenix Project: A Novel about IT, DevOps, and Helping Your Business Win (http://itrevolution.com/books/phoenix-project-devops-book/) - How DevOps techniques can fix the problems that happen in IT organizations.
⟡ The Practice of System and Network Administration
 (http://everythingsysadmin.com/books.html) - 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 (http://www.itpi.org/the-visible-ops-handbook-review.html) - Is a methodology designed to jumpstart implementation of controls and process improvement.
⟡ UNIX and Linux System Administration Handbook (http://www.admin.com/) - Approaches system administration from a practical perspective.
⟡ Securing DevOps
 (https://manning.com/books/securing-devops?a_aid=securingdevops&a_bid=1353bcd8) - A book on Security techniques for DevOps that reviews state of the art practices used in securing web applications and their infrastructure.

Newsletters

⟡ Servers for Hackers (http://serversforhackers.com/) - Newsletter for programmers who find themselves needing to know their way around a server.
⟡ DevOpsLinks (http://devopslinks.com) - A community of DevOps, SysAdmin & Developers with a weekly newsletter and a team chat.

Repositories

Debian-based distributions.

⟡ Dotdeb (http://www.dotdeb.org/) - Repository with LAMP updated packages for Debian.

RPM-based distributions.

⟡ ElRepo (http://elrepo.org/tiki/tiki-index.php) - Community Repo for Enterprise Linux (RHEL, CentOS, etc).
⟡ EPEL (https://fedoraproject.org/wiki/EPEL) - Repository for RHEL and compatibles (CentOS, Scientific Linux).
⟡ Remi (http://rpms.famillecollet.com/) - Repository with LAMP updated packages for RHEL/Centos/Fedora.
⟡ Software Collections (https://www.softwarecollections.org) - Community Release of Red Hat Software Collections (https://access.redhat.com/documentation/en-US/Red_Hat_Software_Collections/). Provides updated packages of Ruby, Python, 
etc. for CentOS/Scientific Linux 6.x.

Websites

Useful sysadmin related websites.

⟡ Ops School (http://www.opsschool.org) - Comprehensive program that will help you learn to be an operations engineer.
⟡ Digital Ocean Tutorials (https://www.digitalocean.com/community/tutorials) - A surprisingly vast resource for getting the basics of certain applications, tools, or even systems administration topics.

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This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International (http://creativecommons.org/licenses/by-sa/4.0/) license.