ClearOS
A very good alternative for Windows Server, for free
22 Alternatives To ClearOS
Amahi Home Server
Amahi is a media, home and app server software known for its easy-to-use user interface. Amahi has the best media, backup and web apps for small networks.
FreeNAS
FreeNAS is a storage operating system strong and robust enough to meet the needs of enterprise level businesses.
IPFire
IPFire is a server distribution with intended to use as a firewall.
IPFire is a hardened, versatile, state-of-the-art Open Source firewall based on Linux. Its ease of use, high performance in any scenario and extensibility make it usable for everyone.
NethServer
NethServer is an operating system for Linux enthusiasts, designed for small offices and medium…
OpenMediaVault
OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
Ubuntu Server
Secure, fast and economically scalable, Ubuntu helps you make the most of your infrastructure. Whether you want to deploy a cloud or a web farm, Ubuntu Server supports the most popular hardware and software.
Univention Corporate Server
Univention Corporate Server UCS with Active Directory functions and App Center is the cost-efficient and popular successor to Microsoft’s server solutions.
Unraid
Simplicity. Flexibility. Scalability. Modularity. Unraid empowers you to build the system you’ve always wanted using your preferred hardware, software, and operating systems.
VyOS
VyOS in an open source Linux-based operating system sold and distributed by Sentrium corporations. It is geared toward IT specialists and network administrators for the purpose of securing network and company data… read more.
Zentyal
Linux directory, domain, mail, gateway and infrastructure server for SMBs.
ZeroShell
Zeroshell is a Linux distribution for servers and embedded devices aimed at providing the main…
pfSense
pfSense is a free and open source firewall and router that also features unified threat management, load balancing, multi WAN, and more
unRAID Server
A scalable, consumer-oriented, server operating system.