KaOS Linux calls itself a "lean KDE Distribution", and it is certainly that, at least in terms of what is actually offered for download. Go to the KaOS Download page and you will find exactly one file (a 1.6GB hybrid Live ISO image) with one desktop (KDE Plasma 5.4) and one architecture (64 bit). No huge 'all-in' 4+ GB installer or tiny 'netinst' core-only installer, no other desktops (not even community editions), and no 32-bit version. Lean and focused.
A new update to OpenIndiana is available, the operating system powered by Illumos that's derived from what was the OpenSolaris code-base prior to it being killed by Oracle. OpenIndiana 2015.10 "Hipster" is the name of this new release.
On October 4, Alexander Pyhalov had the great pleasure of announcing the immediate availability for download of the OpenIndiana 2015.10 (Hipster) open-source Solaris-based operating system.
GNU Hurd – microkernel and part of GNU Project. Hurd means “Hird of Unix-Replacing Daemons”, Hird – “Hurd of Interfaces Representing Depth. Total recursion! Development started in 1990 (before Linux kernel) as part of plans to create fully free and open source operation system. Unlike the Linux kernel Hurd have a lot of system daemons (you can see it on video) run by GNU Mach microkernel and some specific system protocols. Popularity of Linux lowered Hurd’s priority, but project progress all this 25+ years.
RancherOS is a container-native operating system designed solely for running Docker containers. It’s one of 6 operating systems designed just for Docker and other container runtimes in active development.
On an operating system of that nature, you need containers for providing system-wide services other than running applications. They are called system containers in Project Atomic, a container-native OS developed by the folks at Fedora. In this linked-to blogged post, Ivan Mikushin from Rancher, the company developing RancherOS, shows how to use Docker Compose to create such system containers.