[root@webserver:~]# nixos-rebuild switch --upgrade
unpacking channels...
warning: Nix search path entry '/etc/nixos/configuration.nix' does not exist, ignoring
error: file 'nixos-config' was not found in the Nix search path (add it using $NIX_PATH or -I), at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/default.nix:1:60
(use '--show-trace' to show detailed location information)
building Nix...
warning: Nix search path entry '/etc/nixos/configuration.nix' does not exist, ignoring
error: file 'nixos-config' was not found in the Nix search path (add it using $NIX_PATH or -I), at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/default.nix:1:60
(use '--show-trace' to show detailed location information)
building the system configuration...
warning: Nix search path entry '/etc/nixos/configuration.nix' does not exist, ignoring
error: file 'nixos-config' was not found in the Nix search path (add it using $NIX_PATH or -I), at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/default.nix:1:60
(use '--show-trace' to show detailed location information)