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.
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:
- change the Firmware version stated in the file “/etc.defaults/VERSION” to a number lower than the FW version you want to install
- 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
- Download the desired firmware from Synology.
- 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 frombuildnumber="2668"
to
buildnumber="2650"
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. - 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.) 🙂
IT affinity! 
Hi, thanks for your advice. Helped me a lot.
Hey,
That’s a great article. Was really helpful.
Thanks! 🙂
I thing, installation of older package will finished, but no change is made in Synolopgy system. It seems, that no data was overwritten.
Hello,
How can I save old version into the syslog file through Puty ?
When I changed lower version as I wanted to downgrade, in the DSM update console still I see actual version. No changes are saved !
Then I could not downgrade firmware.
Thank you for your advice.
I’m stuck. This is first time I use SSH. I managed to login and open VERSIONS but I don’t know how should I make changes and save it.
I just realized I need to login as ROOT. But my admin password which works for admin user do not work as ROOT user. I tried changing password, without password… I’m getting all the time Access Denied.
By default, root and admin passwords are the same. The Synology Security Advisor urges you to change those (for a good reason). So maybe you changed it and hopefully still remember your root password. If not, let me google that for you: https://www.synology.com/en-global/knowledgebase/DSM/tutorial/General/How_do_I_log_in_if_I_forgot_the_admin_password
If you’re new to the console the vi editor as used in my example is probably a bit intuitive. Still, you’ll find plenty of help using it on the internet. Another option (better for beginners) is the nano editor. Give it a go, it’s pretty much self-explanatory:
nano /etc.defaults/VERSION