[root@nixos:~]# nix-channel --update
these derivations will be built:
/nix/store/r68zsc8pp9snv7bm0gvz2gzbi1fgrjl9-nixos-hardware.drv
building '/nix/store/r68zsc8pp9snv7bm0gvz2gzbi1fgrjl9-nixos-hardware.drv'...
unpacking channels...
created 6 symlinks in user environment