NixOS is a Linux distribution built on top of the Nix package manager. It uses declarative configuration and allows reliable system upgrades. Two main branches are offered: current Stable release and Unstable following latest development. Although NixOS started as a research project, it is a fully functional and usable operating system.[citation needed] NixOS has tools dedicated to DevOps and deployment tasks.

A stamp an embassy or consulate puts on a visa when there is a mistake in the visa or the visa is a duplicate visa (two of the same kind). It does not affect the validity of other visas in the ...