Revert My Cloud OS5 Back to OS3 (EX4100, EX2 Ultra & Mirror G2)

Many people have upgraded to My Cloud OS5, only to discover that it’s not suitable for their needs. WD claims that OS5 can’t be reverted, but that’s simply not true.

The “Safe Mode” firmware appears to be unchanged by OS5, so reverting back to OS3 can be accomplished by deleting the Linux kernel and system configuration files to trigger “Safe Mode” after rebooting the NAS. Deleting the Linux kernel may sound scary, but it’s exactly what the firmware does to trigger “Safe Mode” if it detects a problem.

An SSH connection is required, and this specific process of reverting back to OS3 only works on the My Cloud EX4100, My Cloud EX2 Ultra, or My Cloud Mirror Gen 2. It should NOT be attempted on any other NAS model. I’ve personally tested it on the My Cloud EX2 Ultra, and know for a fact that it works, but I don’t use the cloud-based services, so I don’t know how they might be affected. Use at your own risk.

The processs of reverting back to OS3 causes all users except “admin” to be lost, in addition to all system settings. Shares and data should remain unaffected. If the OS3 system configuration settings were saved to a file prior to upgrading to OS5, it should be possible to restore them via the dashboard.

Settings / Utilities / System Configuration / Import File

Create backups of your data, enable SSH access from the dashboard, then shut down the NAS and remove all hard drives, being certain to label each drive so it can be reinserted in the same bay it came from. This done as a precaution, where the drives can be reintegrated afterwards, with no data loss.

Download the My Cloud OS3 firmware for your NAS from the WD website, and save it to your computer. Be certain to verify that you have the correct My Cloud OS3 firmware bin file before proceeding.

Power on the NAS, then connect via SSH and log in (user: sshd) to get a Linux command prompt. An SSH client such as Putty is required. Execute the following commands, which will erase the Linux kernel and system settings, thus triggering the “Safe Mode” after a reboot, where new firmware may be uploaded. The commands must be executed ONE LINE AT A TIME , not all at once.

Erase Linux Kernel:

flash_eraseall /dev/mtd1

Erase Config Files:

umount -l /usr/local/config
ubidetach /dev/ubi_ctrl -m 5
flash_eraseall /dev/mtd5

WARNING: Carefully type the commands exactly as shown above, and DO NOT use the Linux dd command. Also, don’t touch /dev/mtd0 or /dev/mtd4. The following is is a list of the NAND partitions, for reference only.

/dev/mtd0 "U-Boot"
/dev/mtd1 "uImage"
/dev/mtd2 "uRamdisk"
/dev/mtd3 "image.cfs"
/dev/mtd4 "rescue fw"
/dev/mtd5 "config"
/dev/mtd6 "reserve1"
/dev/mtd7 "reserve2"

Simply power off the NAS, then power it on again, giving it time to finish booting into “Safe Mode”. Afterwards, connect to it via a web browser using the IP address. A “Safe Mode” firmware upload page should become available, where you can manually upload the OS3 firmware, as appropriate for your NAS.

WARNING: If you assigned a static IP address using the NAS, it won’t work because it was erased when the config files were deleted as part of the reversion process. The NAS will be assigned a new IP address by the router via DHCP. Log into the router and determine what the new IP address is, then use that to connect to the NAS with a browser. If you have trouble uploading new firmware, try a different browser.


After uploading the OS3 firmware, and the NAS has finished rebooting, power it off again and reinsert the hard drives. Power on the NAS, where all installed hard drives should now have a red status light after the boot process has finished. Connect to the dashboard via a web browser using the IP address and a “RAID Roaming” message should appear after logging in. Click “OK” to integrate the hard drives, without data loss. Afterwards, the status light for each installed hard drive should turn blue.

The process is now complete.


Just completed this procedure on my EX2 Ultra.
Worked a treat.
Thank you very much for this guide

Anyone try this with an EX4100? Having so many issues with 5 I would really like to give this a try but don’t want to brick my NAS.

My Cloud EX2 Ultra success back to OS3 :+1:

Than you for your manual! :sunglasses:

I would stay with the old OS3. WD said the OS5 is an upgrade. However, so far from what I see, it even has less features than the OS3 :roll_eyes:

Hello DSWV42,
followed your instructions step by step, but it didn’t work on my EX4100… :frowning:
Now I have a blinking red light and a message FIRMWARE UPDATE FAILED.
What can I do?

First, exactly what steps did you perform? Did you download the correct firmware version? Here’s a direct link:


The process has been tested and is known to work, so something must have went wrong. You should be able to access the “Safe Mode” page using the browser and the device IP address, as outlined in the instructions. Try again after downloading the firmware again, and see if it works.

I didn’t get to that point.
After accessing in SSH mode via Putty and copy/pasting/executing the commands that you indicated, I have turned the NAS off and then back on and the error code appeared.
The NAS doesn’t get any IP address now, so it’s unreachable through browser :frowning:

The “FIRMWARE UPDATE FAILED” message is part of the “Safe Mode” firmware, which is programmed to say that. So far, it’s doing exactly what it should be doing, and the next step is uploading new firmware, except that it appears that you have a networking issue.

Check your router, the “Safe Mode” firmware gets an IP address using DHCP, is it enabled at the router?

the DHCP is of course enabled at the router, but I had chosen to gıve the NAS a statical IP address (on the LAN), which is now unreachable.

That may be the source of your problem. Disable the static IP address assignment, and allow DHCP to assign an IP address, then use it to connect via the browser.

but how and where? because that setting was made in the NAS parameters, which are now not accessible anymore…

If you assigned a static IP address using the NAS, that won’t work because it was erased when the config files were deleted as part of the reversion process. The NAS has a new IP address now, as assigned by the router using DHCP. Log into the router and determine what the new IP address is, then use that to connect to the NAS using the browser.

Maybe you have to delete the old wd-device (with the static ip) in your router.

done that, thanks, but when I turn the NAS back on, it keeps telling:
IP address: disconnected

Ignore the LCD display for now. Did you get the new IP address and try connecting via a browser? Note that it may get a different IP address every time it’s rebooted.

If you still can’t connect, try shutting down the NAS and removing the power cord for a few minutes. Then replace the power cord, turn it on, and try again after the “Safe Mode” firmware finishes booting.

Tried that several times.
I have also disconnected all other devices from router, leaving only PC and NAS, but this one doesn’t “appear” when turned on.

I’m still convinced that it’s a networking issue, but routers are so varied that I can’t give specific advice about them. The NAS “Safe Mode” firmware appears to be booting exactly as it should, and is simply waiting for new firmware to be uploaded.

Have you tried rebooting your router, or tried connecting the network cable to a different port on the NAS and/or router?

tried using the second port present on NAS, tried changing port on router, tried changing cable…
the NAS doesn’t pop up among the devices connected to the LAN