Looking for “NAS540_521AATB3C0_Upgradekey.zip” – original download link no longer working

Martin75

Hello everyone,

I am looking for help recovering my Zyxel NAS540 back to the original stock firmware.

Some time ago, I installed Debian/OMV on the device. Now I would like to completely restore the original Zyxel firmware (V5.21(AATB.11)C0).
However, the usual USB-recovery / “Upgradekey” method seems to be impossible because the download link mentioned in several older forum posts is no longer accessible:

https://zyxel.diskstation.eu/Users/Mijzelf/RescueSticks/NAS540_521AATB3C0_Upgradekey.zip

Unfortunately, this link appears to be offline or unreachable.

I am specifically looking for:

NAS540_521AATB3C0_Upgradekey.zip
(or any working RescueStick package for NAS540 with ras.bin, uImage, uInitrd, etc.)

If someone still has this file and can provide a working download link or mirror, I would be extremely grateful.
My goal is simply to restore the stock firmware; the data on the device is not needed.

@Mijzelf — if you happen to see this:
Several users reported that your RescueSticks worked perfectly in the past. If you can re-upload the NAS540 version or send a link, that would be greatly appreciated.

Thank you very much in advance!
Best regards,

Martin

stein_990

https://web.archive.org/web/20230909074225/https%3A//zyxel.diskstation.eu/Users/Mijzelf/RescueSticks/

stein_990

https://web.archive.org/web/20230909074225/https%3A//zyxel.diskstation.eu/Users/Mijzelf/RescueSticks/

Martin75

Hi again,
thanks a lot for the link you provided earlier.
Unfortunately I have just checked the content, and it seems that this is only a minimal update package, not the full USB recovery Upgradekey.

My USB stick currently contains only:

salted_checksum
usb_key_func.sh
nas5xx_check_file
readme
flash.log
nas5xx_fw/ (contains only ras.bin and ras.bin.md5sum)

Because of my current situation (NAS540 stuck in Barebox, watchdog reboots, no network, no bootable firmware), I absolutely need the complete Upgradekey package, including:

• zld
• uImage
• rd.gz
• romfile
• full boot scripts (upgrade.sh, init-usb.sh, etc.)
• all md5 files
• the entire directory structure

Only the full Upgradekey allows the NAS to boot into the rescue environment before the watchdog triggers, disable it, and reflash the NAND.

Could you (or someone else) please provide the full NAS540 Upgradekey package?
The minimal one cannot be used for recovery from my current state.

Thank you very much!

Martin

Mijzelf

I'm not aware of any such package. The package you downloaded is the one provided by ZyXEL. The ras.bin file contains most of the files you mention.

The shell script is executed by the booted kernel+initramfs, before it loads and mounts the rootfs from flash. AFAIK on that moment there is no watchdog. When using a blocking script the box doesn't reboot.