diff --git a/install.sh b/install.sh
index 35b8207..9d76586 100755
--- a/install.sh
+++ b/install.sh
@@ -1,38 +1,65 @@
-#!/bin/bash
+#!/usr/bin/env bash
+
+function install_pkg() {
+  if hash apt-get 2>/dev/null; then
+    sudo -n apt-get update
+    sudo -n DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends ${$}
+    return
+  fi
+
+  if hash nix 2>/dev/null; then
+    echo "INSTALL ${@} yourself with nix"
+    return
+  fi
+}
 
 function setup_ssh() {
+  configfile=~/.ssh/config
+  if grep -Fxq "# dotfiles installed" ${configfile}; then
+    return
+  fi
+
   mkdir -p ~/.ssh
-  touch ~/.ssh/config
-  chmod 644 ~/.ssh/config
-  cat << EOF >> ~/.ssh/config
+  touch ${configfile}
+  chmod 644 ${configfile}
+  cat << EOF >> ${configfile}
 Include ${HOME}/dotfiles/ssh.config
+# dotfiles installed
 EOF
 }
 
 function setup_git() {
-  cat << EOF > ~/.gitconfig
+  configfile=~/.gitconfig
+  if grep -Fxq "# dotfiles installed" ${configfile}; then
+    return
+  fi
+
+  cat << EOF > ${configfile}
 [include]
   path = ${HOME}/dotfiles/git/gitconfig
 [core]
   excludesfile = ${HOME}/dotfiles/git/gitignore_global
+# dotfiles installed
 EOF
 
   setup_ssh
 }
 
 function setup_tmux() {
-  sudo -n apt-get update
-  sudo -n DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-    tmux
-  cat << EOF > ~/.tmux.conf
+  configfile=~/.tmux.conf
+  if grep -Fxq "# dotfiles installed" ${configfile}; then
+    return
+  fi
+
+  install_pkg tmux
+  cat << EOF > ${configfile}
 source ${HOME}/dotfiles/tmux/tmux.conf
+# dotfiles.installed
 EOF
 }
 
 function setup_fish() {
-  sudo -n apt-get update
-  sudo -n DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-    fish
+  install_pkg fish
 
   USER=`whoami`
   sudo -n chsh $USER -s $(which fish)
@@ -45,9 +72,7 @@ function setup_fish() {
 }
 
 function setup_nvim() {
-  sudo -n apt-get update
-  sudo -n DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-    neovim
+  install_pkg neovim
   mkdir -p ~/.config/nvim/
   ln -s ~/dotfiles/init.vim ~/.config/nvim/init.vim
 
@@ -60,10 +85,10 @@ function setup_nvim() {
 
 function main() {
 
-  sudo apt-get install locales less
+  install_pkg locales less
 
-  echo "sv_SE.UTF-8 UTF-8" | sudo tee -a /etc/locale.gen
-  sudo locale-gen
+  #echo "sv_SE.UTF-8 UTF-8" | sudo tee -a /etc/locale.gen
+  #sudo locale-gen
 
   setup_fish
   setup_ssh