NAS: Downgrading DSM (DS213+)

As mentioned before, Synology’s update from Diskstation Manager 4.1-2657 to DSM 4.1-2668 made the issue where files in the encrypted shared folders were case-sensitive reappear. As this rendered the NAS almost useless to me, my best possibility was to downgrade DSM.

Officially, downgrading is not possible at all.

The DSM version is not downgradeable
The DSM version is not downgradeable

As (almost) always, the Internet provides a couple of workarounds. However, after skimming through a couple of them, downgrading seemed pretty risky to me, considering the risk of damaging my device or even losing my whole data.
But I didn’t give up and finally found a really comfortable solution here:

  1. change the Firmware version stated in the file “/etc.defaults/VERSION” to a number lower than the FW version you want to install
  2. Use the Web page management GUI to install the desired Firmware.

Here’s a bit more detailed description. Please note that you do the downgrading at your own risk, as it is not officially supported!

Three Steps to downgrade your DSM

  1. Download the desired firmware from Synology.
  2. SSH to your DSM and run
     vi /etc.defaults/VERSION

    then change the buildnumber/version to a lower version, than the one you’re trying to install.
    For example: I changed from




    because I wanted to downgrade from 2668 to 2657.
    If this step is skipped DSM will refuse to install the “new” (that is old) firmware.

    Unable to perform DSM update because this DSM is an older version.
    Unable to perform DSM update because this DSM is an older version.
  3. Log on to your DSM’s webinterface, click Control Panel | DSM Update | Manual DSM Update. Then choose the firmware and downgrade your DSM.

(4. File any bug that made you downgrade at Synology.) 🙂