DS420j. Dead usb-DOM

Hi all. I have DS420j which is not booting after installing OS.

The operating system installs without errors, then the device says that it needs to reboot and turns on the timer for 10 minutes in the web interface.
After this time, the web interface writes that something went wrong. If I reboot by turning off the power, after loading it says that the operating system needs to be reinstalled.
I connected via the serial console, the device constantly gives an error: "usb usb5-port1: Cannot enable. Maybe the USB cable is bad?" Based on the symptoms, it looks like the bootable flash has died. The problem is that in my case it is soldered onto the board.
After reviewing a bunch of posts on the Internet, I decided that I had found a solution - find a USB flash drive, change “VID” and “PID” to F400 on it, find a synoboot image somewhere and load it onto the flash drive then boot from it. Unfortunately, I failed - when I logged into the same working machine via SSH, I did not see synoboot in /dev.
What other recovery options are possible?

I don't have any idea about this DS420j box. It's a Realtek RTD1296. But I recall there were some threads here about this SoC. Please search the forum.

-bodhi
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Ah. Here is the thread:

https://forum.doozan.com/read.php?2,135588,135872#msg-135872

-bodhi
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Hi! Thanks for link. I figured out that the firmware of my NAS is located on /dev/mtdX (X=0 - 6). So, I dumped this dev with dd. Thats what i got:

mtd0.dump: Device Tree Blob version 17, size=56175, boot CPU=0, string block size=2415, DT structure block size=45416
mtd1.dump: u-boot legacy uImage, kernel 69057, Linux/ARM 64-bit, OS Kernel Image (Not compressed), 2706146 bytes, Fri Jan 12 09:04:10 2024, Load Address: 0x0B000000, Entry Point: 0x0B000000, Header CRC: 0x2986B9F7, Data CRC: 0x043B0251
mtd2.dump: u-boot legacy uImage, ramdisk 69057, Linux/ARM 64-bit, RAMDisk Image (Not compressed), 3958257 bytes, Fri Jan 12 09:14:45 2024, Load Address: 0x02200000, Entry Point: 0x02200000, Header CRC: 0x9B91710A, Data CRC: 0x66B12A43
mtd3.dump: data
mtd4.dump: u-boot legacy uImage, kernel 25556, Linux/ARM 64-bit, OS Kernel Image (Not compressed), 2982190 bytes, Mon Jul  5 06:00:58 2021, Load Address: 0x0B000000, Entry Point: 0x0B000000, Header CRC: 0xEF40F1D4, Data CRC: 0xB45133E7
mtd5.dump: u-boot legacy uImage, ramdisk 25556, Linux/ARM 64-bit, RAMDisk Image (Not compressed), 3756961 bytes, Mon Jul  5 11:34:14 2021, Load Address: 0x02200000, Entry Point: 0x02200000, Header CRC: 0x3B73718A, Data CRC: 0xD6C99F45
mtd6.dump: data

Now i think i need somehow mount the image (which one do i need?) to edit the grub.cfg, to set the boot device (usb stick instead the dead DOM), right?
Im not very good at linux and firmware stuff, but it seems to be interesting experience. I will be grateful if you tell me which direction to go.

> Now i think i need somehow mount the image (which
> one do i need?) to edit the grub.cfg, to set the
> boot device (usb stick instead the dead DOM),
> right?

This ARM device does not use Grub, the boot loader is u-boot.

> Im not very good at linux and firmware stuff, but
> it seems to be interesting experience. I will be
> grateful if you tell me which direction to go.

Unfortunately I have not built kernel for this RTD1296 SoC (I don't have any REALTEK NAS), so I'm not familiar with either stock FW on this box or how to recover from a bad stock FW installation.

Usually when we troubleshoot an ARM based NAS like this, the 1st thing is to connect a serial console, and watch the u-boot progress on serial console to see where the problem occurs.

Many NAS also have a rescue mechanism using a USB thumb drive (that's where the rescue FW stored). You can either find it at Synology website or contact Synology support for info where to download this rescue FW.

-bodhi
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Hi. I logged the OS installation process:
When i install OS, before reboot (boot-with-sata.txt)
It seem like system cant reboot, infinite spam with usb error. I can ping NAS but nothing more.
Then i unplug power supply, plug it again and power on NAS (boot-with-sata-after-reboot.txt). Spamming with usb error again.

Hi. My problem was solved in a very unusual way. I decided to downgrade the DSM version to 6 for the reason that for this version its easier to find tools for editing images. After installing the system and the usual reboot by turning off the power, I was surprised to see a USB-DOM mounted in the console!
After that, the system loaded everything it needed and booted in normal mode!
Then i tried to update the system to version 7 and the USB-DOM fell off again. After returning to version 6, everything worked again.