[root@nas:~]# nixos-rebuild  switch
building Nix...
warning: unknown setting 'signed-binary-caches'
warning: unknown setting 'signed-binary-caches'
building the system configuration...
warning: unknown setting 'signed-binary-caches'
trace: warning: The option `ip4' defined in `/etc/nixos/configuration.nix' has been renamed to `ipv4.addresses'.
these derivations will be built:
  /nix/store/liig8z4rps556kchg54db7i16z8363yq-closure-info.drv
  /nix/store/i34fcsmrj1rga7rfwpf02ayiyrvmhj3h-squashfs.img.drv
  /nix/store/yi673m3zhn20y5hd77wkfp3mvzhfj7qb-initrd.drv
  /nix/store/0hb03xri84hr679pxyzbpdma0qyslp9b-grub-config.xml.drv
  /nix/store/9655p7pgwl571dzjv984xypny9i9pf2d-install-grub.sh.drv
  /nix/store/sfdzr0hxwrqzqap40cs2lihjswgfw32g-nixos-system-nas-18.03.133004.a1299c9951b.drv
building path(s) ‘/nix/store/mwav7kdam1jja3lhpq4l4smahzmd3cg7-closure-info’
/nix/store/aj9rz4k3xvg8q9fzqfnb0q123707zp0n-builder: line 1: .attrs.sh: No such file or directory
builder for ‘/nix/store/liig8z4rps556kchg54db7i16z8363yq-closure-info.drv’ failed with exit code 1
cannot build derivation ‘/nix/store/i34fcsmrj1rga7rfwpf02ayiyrvmhj3h-squashfs.img.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/yi673m3zhn20y5hd77wkfp3mvzhfj7qb-initrd.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/0hb03xri84hr679pxyzbpdma0qyslp9b-grub-config.xml.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/9655p7pgwl571dzjv984xypny9i9pf2d-install-grub.sh.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/sfdzr0hxwrqzqap40cs2lihjswgfw32g-nixos-system-nas-18.03.133004.a1299c9951b.drv’: 1 dependencies couldn't be built
error: build of ‘/nix/store/sfdzr0hxwrqzqap40cs2lihjswgfw32g-nixos-system-nas-18.03.133004.a1299c9951b.drv’ failed

[root@nas:~]# nix-channel --list
nixos-17.09 https://nixos.org/channels/nixos-17.09
nixos https://nixos.org/channels/nixos-18.03