anchor.diff:        echo -n .
         ${coreutils}/bin/sleep 1
       done
  +    ${coreutils}/bin/touch /xchg/waiting_done
       echo " success."
   
       ${openssh}/bin/ssh \
  
positive.code:       # Print a dot every 10 seconds only to shorten line length.
        ${coreutils}/bin/sleep 10
      done
      echo " success."
      # Loop forever, because this VM is going to be killed.
      ${loopForever}
  
negative.code:   ];
  
    controllerQemuArgs = concatStringsSep " " (maybeKvm64 ++ [
      "-pidfile $CTRLVM_PIDFILE"
      "-nographic"
      "-no-reboot"
      "-virtfs local,path=/nix/store,security_model=none,mount_tag=store"
  