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Boot Issues Recovery

Warning

This page might be out of date, if you need assistance, please come ask in the Rinkhals Discord

If you messed up your file structure playing with your printer, you might end up (soft) bricking your printer. In my situation, my printer refused to start, only showing the Anycubic logo with an empty progress bar but nothing more. Some of the system files needed to start were missing, without any possibility of using SSH or ADB in software.

It is possible to recover from this situation and restore the partitions to a bootable state.

You will need to build a special USB cable and access to a Linux machine (Windows might work but neither confirmed nor documented yet).

Mainboard connection

Follow the guide on this page: Mainboard connection

Restore broken partitions

I uploaded a copy of working partitions to ease the recovery process. It uses 2.3.5.3 firmware and I deleted / changed all the device-specific keys, you will need to provide/restore yours in the files listed below (in the userdata and useremain partitions).

Link to partition backup: 2.3.5.3

userdata partition

I managed to recover form a deletion of everything in the userdata partition. This one contains all the startup scripts for your printer to boot and to start Klipper, the UI, everything.

I took the last official update package (2.3.5.3 at the time of writing).

  • Unzip the .swu file with this password U2FsdGVkX19deTfqpXHZnB5GeyQ/dtlbHjkUnwgCi+w=
  • Extract the setup.tar.gz file
  • There is a update_shell/update_udisk_init.sh script, responsible (I guess) to initialize everything from the update itself

I then modified the script to use the path of my partition being modified, and removed all the unecessary parts:

update_file_path="./update_swu"
to_update_path="./_userdata/app/gk"
to_update_wifi_cfg="./_userdata/wifi_cfg"
to_run_sh_path="./_userdata/app/kenv"

I ran the modified script, made sure all the necessary files are present, including specifically:

  • /userdata/app/kenv/run.sh
  • /userdata/app/gk/start.sh
  • /userdata/app/gk/gkapi, gkcam, gklib and K3SysUi
  • /userdata/app/gk/device.ini

Check that all your machine-specific files are present:

  • /userdata/app/gk/config/device.ini
    • [cloud_prod] and [cloud_global_prod] / mechineCode, deviceUnionId and deviceKey should be filled properly
  • /userdata/app/gk/config/device_account.json
    • deviceId, username and password should be filled properly
    • deviceId must be the same as /useremain/dev/device_id
  • /useremain/app/gk/cert1 and /useremain/app/gk/cert3
    • Printer-specific certificates

Then I wrote back the partition to the motherboard, plugged everything back, and it worked!

Here is a copy of the modified script I used: reset_userdata.zip

useremain partition

Until I have a proper guide, check: https://github.com/Bushmills/Anycubic-Kobra-3-rooted/discussions/5#discussioncomment-11504611

Other partitions

The other partitions are directly available from the official .swu files:

  • Unzip the .swu file with this password U2FsdGVkX19deTfqpXHZnB5GeyQ/dtlbHjkUnwgCi+w=
  • Extract the setup.tar.gz file
  • Extract the update_ota.tar file

You will see 5 .img files.

Those are partition dumps of the other partition you can flash using the method above.