AlmaLinux OS
AlmaLinux OS is an open-source, community-driven project that is built from the source code of Red Hat Enterprise Linux (RHEL). AlmaLinux is a completely binary compatible fork of RHEL and it is maintained by AlmaLinux OS Foundation which is a register non-profit.
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SmartOS
SmartOS is an open-source UNIX-like operating system based on illumos, a community fork of OpenSolaris. It features four technologies - ZFS (a combined file system and logical volume manager), DTrace (a dynamic tracing framework for troubleshooting kernel and application problems), Zones (a lightweight virtualisation solution), KVM and bhyve (two full virtualisation solutions for running a variety of guest operating systems, including Linux, Windows, BSD and Plan9).