To install NixOS behind a proxy, do the following before running nixos-install. Update proxy configuration in /mnt/etc/nixos/configuration.nix to keep the internet accessible after reboot. networking.proxy.default = "http://user:password@proxy:port/"; networking.proxy.noProxy = "127.0.0.1,localhost,internal.domain"; Setup the proxy environment variables in the shell where you are running nixos-install. # proxy_url="http://user:password@proxy:port/" # export http_proxy="$proxy_url" # export HTTP_PROXY="$proxy_url" # export https_proxy="$proxy_url" # export HTTPS_PROXY="$proxy_url" If you are switching networks with different proxy configurations, use the specialisation option in configuration.nix to switch proxies at runtime. Refer to for more information.