Add setup notes on resizing an LVM LV

notes/nixos-setup.txt

@@ -36,3 +36,9 @@ curl https://git.cryto.net/joepie91/morph-rc/raw/master/data/dummy-configuration
 nixos-install
 
 # NOTE: Don't forget to set a better root password over SSH after restarting
+
+
+#################################
+
+# Resize LV to maximum available space:
+lvresize --resizefs -l +100%FREE /dev/vg_main/lv_root