d22b3ed4bc
See https://www.redhat.com/sysadmin/fedora-31-control-group-v2 for details on why this is desirable, and how it impacts containers. Users that need to keep using the old cgroup hierarchy can re-enable it by setting `systemd.unifiedCgroupHierarchy` to `false`. Well-known candidates not supporting that hierarchy, like docker and hidepid=… will disable it automatically. Fixes #73800
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at https://nixos.org/nixos and in the manual in doc/manual.