add speedtest filesystem helper

utilities/nixos-installers/flake.nix

@@ -24,6 +24,7 @@
       };
 
       # Build a NixOS system that is an installation ISO with SSH enabled and bcachefs
+      # nix build .\#packages.x86_64-linux.iso-minimal-stable
       minimal =
         { nixpkgs, system }:
         nixpkgs.lib.nixosSystem {
@@ -50,6 +51,18 @@
                   # Required as a workaround for bug
                   # https://github.com/NixOS/nixpkgs/issues/32279
                   keyutils
+
+                  (pkgs.writeShellScriptBin "speedtest_fs" ''
+                    dir=''$(pwd)
+                    drive=$(df -h ''${dir} | awk 'NR==2 {print $1}')
+                    echo Testing read speeds on drive ''${drive}
+                    sudo hdparm -Tt ''${drive}
+                    test_file=''$(date +%u%m%d)
+                    test_file="''${dir}/speedtest_fs_''${test_file}"
+                    echo
+                    echo Testing write speeds into test file: ''${test_file}
+                    dd if=/dev/zero of=''${test_file} bs=8k count=10k; rm -f ''${test_file}
+                  '')
                 ];
                 boot.supportedFilesystems = [ "bcachefs" ];