NixOS

NixOS's entire system state -- every installed package, every running service, every desktop and kernel setting -- is described declaratively in Nix configuration files rather than assembled through a sequence of imperative install/configure commands, meaning the exact same configuration file reliably reproduces the exact same system on any machine. Every generation of the system configuration is kept on disk and selectable at boot, so rolling back from a bad configuration change is as simple as booting the previous generation rather than trying to manually undo whatever went wrong. This model has a genuinely steep learning curve distinct from any conventional distribution's package manager, but it's earned a devoted following among developers specifically for eliminating 'works on my machine' configuration drift between systems.