LDAP

• FreeRADIUS - High performance and highly configurable multi-protocol policy/authentication server, supporting RADIUS, DHCPv4 and VMPS.
• OpenDJ - Fork of OpenDS.
• OpenDS - Another directory server written in Java.

Tools and web interfaces

• Indieauth - Sign in with your domain name (using the rel-me-auth protocol).
• Libravatar - Libravatar is a service which delivers your avatar (profile picture) to other websites.
• LDAP Account Manager (LAM) - Web frontend for managing entries (e.g. users, groups, DHCP settings) stored in an LDAP directory.
• OpenID Connect - Simple Identity layer on top of OAuth 2.0.
• OSIAM - Secure identity management solution providing REST based services for authentication and authorization.
• Samba - Active Directory and CIFS protocol implementation.
• BounCA - Personal SSL Key / Certificate Authority web-based tool for creating self-signed certificates.

• Ralph - Asset management, DCIM and CMDB system for large Data Centers as well as smaller LAN networks.
• Snipe IT - Asset and license management software.
• OCS Inventory NG - Enables users to inventory their IT assets.

Client management

• Chocolatey - Windows CLI package manager written in .NET/PS, based on [NuGet](https://www.nuget.org/).
• just-install - Python script for downloading and silently installing MSI files.
• WAPT - Network-wide (un)installation, configuration and upgrades of Windows based software.
• WPKG - Software deployment, upgrade and removal program for Windows.

Client management

• rclone - Command line program to sync files and directories to and from several cloud storage systems/providers.
• Duplicity - Encrypted bandwidth-efficient backup using the rsync algorithm.
• Restic - Secure, remote backup tool. Designed to be easy, fast, verifiable and efficient.
• UrBackup - Another client-server backup system.
• ZBackup - Versatile deduplicating backup tool.

Client management

• HPCBIOS - Effort to setup a common, well-documented and reproducible environment spanning across multiple HPC systems and sites, *inclusive* of documentation.
• Spack - Flexible package manager that supports multiple versions, configurations, platforms, and compilers.

Build automation

• GNU Make - Most popular automation build tool for many purposes.
• Apache Ant - Automation build tool, similar to make, written in Java.

Build automation

• Hubot - Customizable, life embetterment robot.
• Lita - Robot companion for your company's chat room.

Build automation

• OpenStack - Build private and public clouds.
• Eucalyptus - Private cloud software with AWS compatibility.
• Flynn - Open source Platform-as-a-Service (PaaS) for running applications in production.

Build automation

• Cloud Foundry - Platform-as-a-Service suite to provide the orchestration services that make distributed apps a powerhouse of awesomeness.
• StackStorm - Event Driven Operations and ChatOps platform for infrastructure management. Written in Python.
• Terraform - Terraform works with many cloud providers and creates infrastructure from code.
• BOSH - IaaS orchestration platform originally written for deploying and managing Cloud Foundry PaaS, but also useful for general purpose distributed systems.

Build automation

• Gerrit - Based on the Git version control, it facilitates software developers to review modifications to the source code and approve or reject those changes.
• Review Board - Available as free software under the MIT License.

Build automation

• Bolt - Open source task orchestration tool useful for automating the manual work it takes to maintain IT infrastructure.
• CFEngine - Lightweight agent system. Configuration state is specified via a declarative language.
• Salt - It's written in Python.

Build automation

• Concourse - Concourse is a CI tool that treats pipelines as first class objects and containerizes every step along the way. ([Demo](https://ci.concourse-ci.org/), [Source Code](https://github.com/concourse/concourse)) `Apache-2.0` `Go`
• GolangCI - Open Source automated code review service for Go integrated with GitHub pull requests. ([Source Code](https://github.com/golangci/golangci)) `AGPL-3.0` `Go`
• werf - Open Source CI/CD tool for building Docker images and deploying to Kubernetes via GitOps. ([Source Code](https://github.com/werf/werf)) `Apache-2.0` `Go`
• PHPCI - Free and open source continuous integration specifically designed for PHP. ([Source Code](https://github.com/block8/phpci)) `BSD-2-Clause` `PHP`

Build automation

• OpenAFS - Distributed network file system with read-only replicas and multi-OS support.
• Ori Filesystem - Secure distributed file system built for offline operation.
• Perkeep - Set of open source formats, protocols, and software for modeling, storing, searching, sharing and synchronizing data, formerly known as Camlistore.
• TahoeLAFS - Secure, decentralized, fault-tolerant, peer-to-peer distributed data store and distributed file system.
• Ceph - Distributed object store and file system.

DNS control panels

• Atomia DNS - DNS management system.
• Pi-hole - Blackhole for Internet advertisements with a GUI for managing and monitoring.
• Poweradmin - Friendly Web-based DNS administration tool for PowerDNS server.

DNS servers

• CoreDNS - Flexible DNS server written on Go.
• djbdns - Collection of DNS applications, including tinydns.
• Designate - DNS REST API that support several DNS servers as its backend.
• Knot - High performance authoritative-only DNS server.
• PowerDNS - DNS server with a variety of data storage back-ends and load balancing features.

Build automation

• Mina - Really fast deployer and server automation tool (rake based).
• munki - Webserver-based repository of packages and package metadata, that allows macOS administrators to manage software installs.
• Rocketeer - PHP task runner and deployment tool.

Build automation

• DrawThe.Net - Javascript tool that uses a YAML-formatted input to programmatically create large, complex, and visually solid diagrams.
• Diagrams.net - Easy to use Diagram UI with a plethora of templates, formerly known as Draw.io.

Domain management

• GNU Emacs - Extensible, customizable text editor-and more.
• Haroopad - Markdown editor with live preview.
• ICEcoder - Code editor awesomeness, built with common web languages.
• Light Table - Next generation code editor.
• Lime - Aims to provide an open source solution to Sublime Text.
• Micro - Modern and intuitive terminal-based text editor.
• Notepad++ - GPLv2 multi-language editor with syntax highlighting for Windows.
• Visual Studio Code - Open source cross-platform extensible code editor from Microsoft.

Tools and web interfaces

• ElasticSearch - Lucene based document store mainly used for log indexing, storage and analysis.
• Flume - Distributed log collection and aggregation system.

Tools and web interfaces

• Mutt - Small but very powerful text-based mail client.

Tools and web interfaces

• Adagios - Web based Nagios interface for configuration and monitoring (replacement to the standard interface), and a REST interface. ([SourceCode](https://github.com/opinkerfi/adagios), [Documentation](https://github.com/opinkerfi/adagios/wiki))
• bolo - Do-it-Yourself monitoring framework built to gather metrics, mine data and report on the systems in your network.
• Healthchecks - Monitoring for cron jobs, background services and scheduled tasks.
• Icinga - Nagios fork that has since lapped nagios several times. Comes with the possibility of clustered monitoring - ([Source Code](https://github.com/Icinga)) - `GPLv2`
• 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.
• PHP Server Monitor - Open source tool to monitor your servers and websites.
• Riemann - Flexible and fast events processor allowing complex events/metrics analysis.
• Sensu - Monitoring framework.
• SWMP - Server Web Monitor Page - Responsive, eye-pleasing Linux server statistics dashboard. ([Source Code](https://github.com/fuzzymannerz/swmp))
• Thruk - Multibackend monitoring web interface with support for Naemon, Nagios, Icinga and Shinken.
• Uchiwa - Simple dashboard for sensu.
• Xymon - Network monitoring inspired by Big Brother.
• Zenoss - Application, server, and network management platform based on Zope.
• NetXMS - Open Source network and infrastructure monitoring and management. ([Source Code](https://github.com/netxms/netxms))
• Cacti - Web-based network monitoring and graphing tool.

Status Pages

• System Status Dashboard (SSD) - Overview about an organization's infrastructure health status.
• Staytus - Staytus is a complete solution for publishing the latest information about any issues with your web applications, networks or services.

Telemetry storage

• Consul - Consul is a tool for service discovery, monitoring and configuration.

Telemetry storage

• Docker Compose - Define and run multi-container Docker applications.
• Docker Swarm - Manage cluster of Docker Engines.
• LXC - Userspace interface for the Linux kernel containment features.
• LXD - Container "hypervisor" and a better UX for LXC.

Telemetry storage

• mtr - Network utility that combines traceroute and ping.
• Wireshark - World's foremost network protocol analyzer.
• Sysdig - Capture system state and activity from a running Linux instance, then save, filter and analyze.

Telemetry storage

• GNU Bazaar - Distributed revision control system sponsored by Canonical.
• Mercurial - Another distributed revision control.

Telemetry storage

• ocserv - Cisco AnyConnect-compatible VPN server.
• OpenVPN - Uses a custom security protocol that utilizes SSL/TLS for key exchange.
• SoftEther - Multi-protocol software VPN with advanced features.
• strongSwan - Complete IPsec implementation for Linux.
• tinc - Distributed p2p VPN.
• WireGuard - Very fast VPN based on elliptic curve and public key crypto.

Hypervisor automation

• Packer - Tool for creating identical (virtual) machine images for multiple platforms from a single source configuration.
• Vagrant - Tool for building complete development environments.

Hypervisors and Virtual Machine Managers/Monitors (VMMs)

• VirtualBox - Free Software type-2 (hosted) virtualization product from Oracle Corporation.
• Xen - Virtual machine monitor for 32/64 bit Intel/AMD (IA 64) and PowerPC 970 architectures.

Virtualization management solutions

• OpenNebula - Simple, but powerful, open source solution to build and manage enterprise clouds.
• OpenVZ Web Panel - Web panel to control OpenVZ virtual machines.
• XCP-ng - Turnkey open source hypervisor platform based on the open source ancestor of Citrix Hypervisor, XenServer.

Telemetry storage

• Riak - Another fault-tolerant key-value NoSQL database.

Telemetry storage

• ActiveMQ - Java message broker.
• Gearman - Fast multi-language queuing/job processing platform.

Telemetry storage

• Firebird - True universal database.
• MariaDB - Community-developed fork of the MySQL.
• adminer - Database management in a single PHP file. ([Source code](https://github.com/vrana/adminer))
• Percona Server - Enhanced, drop-in MySQL replacement.
• PostgreSQL-XL - Scalable PostgreSQL-based database cluster.

Telemetry storage

• Remmina - Feature rich remote desktop application for linux and other unixes.

Web servers

• Apache - Robust, commercial-grade, featureful implementation of an HTTP (Web) server.
• Caddy - Lightweight, general-purpose web server supporting HTTP/2, automatic TLS and easy configuration. Written in Go.
• 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.
• Hiawatha - Prioritises security, simplicity and performance.

Web performance

• HAProxy - Software based load Balancing, SSL offloading and performance optimization, compression, and general web routing.

Web hosting control panels

• Cockpit - Administrator's tool for managing multiple GNU/Linux servers from a single Web-based interface.
• Froxlor - Easy to use panel for Linux with Nginx and PHP-FPM support.
• Virtualmin - Hosting panel for Linux based on webmin.

Web performance

• DevOpsGuys - Devops consultants who blog about operations.
• RoseHosting Blog - Linux tutorials for installing and configuring various software through the Linux command line. Guides and introductions to different Linux technologies and applications. Tips and tricks you can do via the Linux command line and more.

Web performance

• Codex - How to deploy Cloud Foundry PaaS on infrastructures like AWS, OpenStack, Azure by Stark & Wayne, LLC.
• The Linux Command Line - Book about the Linux command line by William Shotts.
• The Visible Ops Handbook: Implementing ITIL in 4 Practical and Auditable Steps - Is a methodology designed to jumpstart implementation of controls and process improvement.

Web performance

• Reddit - Really, really large bulletin board system.
• /r/Linux - News and information about Linux.
• /r/LinuxQuestions
• /r/SysAdmin
• Spiceworks Community - General enterprise IT news and small articles.
• StackExchange Network - Q&A communities.
• Server Fault - StackExchange community for system and network administrators.

Web performance

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

Debian-based distributions

• deb.sury.org - Repository with LAMP updated packages for Debian and Ubuntu.

RPM-based distributions

• IUS - Community project that provides RPM packages for newer versions of select software for Enterprise Linux distributions.
• Software Collections - Community Release of [Red Hat Software Collections](https://access.redhat.com/documentation/en/red-hat-software-collections/). Provides updated packages of Ruby, Python, etc. for CentOS/Scientific Linux 6.x.

RPM-based distributions

• Digital Ocean Tutorials - Surprisingly vast resource for getting the basics of certain applications, tools, or even systems administration topics.

Data dashboards

• 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.
• Netdata - Real-time performance monitoring for Linux systems with plugin support.

Metric collectors

• tcollector - System statistic collection daemon written in Python for OpenTSDB.

Telemetry storage

• OpenTSDB - Store and server massive amounts of time series data without losing granularity.

Telemetry storage

• GestióIP - Automated web based IPv4/IPv6 IP Address Management tool.
• GNS3 - Graphical network simulator that provides a variety of virtual appliances - ([Source Code](https://github.com/GNS3/gns3-gui/), [Documentation](https://docs.gns3.com/)) - `GPLv3`

Telemetry storage

• phpList - Newsletter manager written in PHP.

Web performance

• Servers for Hackers - Newsletter for programmers who find themselves needing to know their way around a server.

Telemetry storage

• awesome-selfhosted/awesome-selfhosted § Project management