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Boot Issues Recovery

Warning

This page documents recovery for a soft-bricked printer. The procedures below range from low-risk (re-flashing a SWU via USB) to high-risk (writing partition images over a mainboard programming connection). Read the whole page before reaching for tools, and ask in the Rinkhals Discord if you are unsure which path applies to your symptoms.

If you modified files on your printer and it now refuses to start, in many cases the printer can be recovered. Typical symptoms include:

  • Anycubic logo with an empty progress bar that never completes
  • Reboot loop before the printer UI loads
  • Touchscreen unresponsive on boot, but the printer's USB networking (if previously enabled) may still appear briefly

If SSH or ADB still respond intermittently, capture logs from /useremain/rinkhals/logs/ before continuing — they will help diagnose what happened and may guide a faster recovery than partition restoration.

Try this first

Before opening the printer, attempt the recovery paths that don't require hardware access:

Re-flash a supported SWU via USB

This is the same path used for normal Rinkhals install/upgrade. If the printer will still mount a USB drive and run an update on boot, this can rebuild enough of the system to get you to a working state.

  1. Download the official Anycubic SWU for your printer model and a supported firmware version (see the model-specific firmware history pages linked from the printers index).
  2. Copy the file to a FAT32 USB drive, renamed to update.swu, inside a folder named aGVscF9zb3Nf.
  3. Plug the USB drive in and power-cycle the printer. Wait for the install sequence (two beeps signals completion on most models).
  4. After the stock firmware comes up, re-install Rinkhals normally.

Restore a partition backup you took earlier

If you ran /opt/rinkhals/tools/backup-partitions.sh from a previous Rinkhals install while the printer was healthy, you have a partition snapshot in /useremain/rinkhals/backups/. Save that snapshot off-device now (before any further tinkering) and use it for partition recovery via the mainboard procedure below. A self-captured backup is always preferable to the generic images linked further down this page because it preserves your printer's machine-specific certificates and identifiers.

If you have not taken a backup and your printer is healthy, stop and do that first. Recovery is far simpler when you have your own known-good partition images.

Restore broken partitions (mainboard-level recovery)

This is the path for printers that won't accept a USB update. It requires a USB-to-mainboard programming connection (a soldered or pogo-pin cable) and access to a Linux machine. Windows may work but is not currently documented.

Mainboard connection

Follow the guide on this page: Mainboard connection

SWU password

Anycubic SWU files are encrypted with a per-model password. The single password that previously appeared on this page only works for K2P, K3, and K3V2; using it on a KS1, KS1 Max, or K3 Max produces a bad password error from unzip with no further explanation. The canonical table is:

Models Password
Kobra 2 Pro, Kobra 3, Kobra 3 V2 U2FsdGVkX19deTfqpXHZnB5GeyQ/dtlbHjkUnwgCi+w=
Kobra S1, Kobra S1 Max U2FsdGVkX1+lG6cHmshPLI/LaQr9cZCjA8HZt6Y8qmbB7riY
Kobra 3 Max 4DKXtEGStWHpPgZm8Xna9qluzAI8VJzpOsEIgd8brTLiXs8fLSu3vRx8o7fMf4h6

This table is mirrored in three places in the Rinkhals source tree and is expected to stay in sync:

  • build/prepare-version.sh (get_printer_swu_password)
  • files/3-rinkhals/tools.sh (get_swu_password, used by install_swu)
  • files/3-rinkhals/opt/rinkhals/ui/common.py (extract_swu)

If you have already sourced Rinkhals' tools.sh (for example, on a different working printer), install_swu <path-to-swu> will pick the correct password automatically based on the model code.

userdata partition

The userdata partition holds the Anycubic startup scripts that boot the printer's UI and Klipper-equivalent stack. A deletion of its contents leaves the printer unable to boot.

Status: documented for Kobra 3 only

The procedure below was captured during a Kobra 3 recovery. Partition layouts and machine-specific paths differ between models. If you successfully recover a different printer, please contribute the steps via PR or share them in Discord so this section can be extended.

The basic shape of the recovery is:

  1. Obtain an official SWU package for your model at a supported firmware version.
  2. Unzip the SWU with the appropriate per-model password (see the table above).
  3. Extract the setup.tar.gz you find inside.
  4. Locate update_shell/update_udisk_init.sh in the extracted tree. This script initializes the partition from update contents.
  5. Modify the script's path variables to write into a mounted copy of the target partition rather than the live one, removing any post-write reboot/finalization steps.
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"

  1. Run the modified script and verify that the expected files are present:

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

  2. Restore the machine-specific files from your records (a partition backup taken from this same printer is the only reliable source for these):

    • /userdata/app/gk/config/device.ini: [cloud_prod] and [cloud_global_prod] sections, with mechineCode, deviceUnionId, and deviceKey filled in
    • /userdata/app/gk/config/device_account.json: deviceId, username, and password. The deviceId must match /useremain/dev/device_id.
    • /useremain/app/gk/cert1 and /useremain/app/gk/cert3: printer certificates

  3. Write the partition image back to the mainboard.

useremain partition

Detailed recovery for the useremain partition is not yet documented in this guide. The Kobra 3 community has a writeup at Bushmills/Anycubic-Kobra-3-rooted discussion #5 that may be helpful for K3 users; other models likely differ.

Other partitions

The remaining partition images are bundled inside the official SWU files:

  1. Unzip the SWU with the appropriate per-model password (see the table above).
  2. Extract setup.tar.gz.
  3. Extract update_ota.tar from inside.
  4. The result contains .img files corresponding to the remaining partitions, which can be written via the same mainboard procedure.

After recovery: prevention

Once the printer is healthy again:

  • Run /opt/rinkhals/tools/backup-partitions.sh while the printer is in a known-good state, and save the resulting snapshot off-device. This gives you the cleanest possible source for future recovery, preserving your printer-specific certificates and identifiers.
  • If you are about to experiment with files on the printer, consider working in /useremain and /userdata/app/gk snapshots first rather than modifying the live filesystem.

Help expand this guide

Recovery details for Kobra 3 Max, Kobra S1, Kobra S1 Max, and Kobra 3 V2 are not currently documented here. If you have recovered any of these models from a soft brick, please contribute the steps via pull request or share them in the Rinkhals Discord so this page can cover the full Kobra family.