Bitcoin Node Corruption Fix Guide

Umbrel on Raspberry Pi 5 (8GB RAM)

The Problem

Your Bitcoin node shows these errors:

[error] OpenUndoFile failed for FlatFilePos(nFile=-1, nPos=0) while reading block undo [error] DisconnectBlock(): failure reading undo data Verification error: irrecoverable inconsistency in block data : Corrupted block database detected. Please restart with -reindex or -reindex-chainstate to recover.

Translation: The blockchain database is corrupted and can't read block data properly.

Quick Fix Steps

1. Check Your Node's Mode

If running pruned mode (saves disk space), you MUST use full -reindex
If running full node, you can try -reindex-chainstate first (faster)

2. Edit Bitcoin Configuration

You can do this two ways:

Method A: Through Umbrel UI (Easiest)

Open your Umbrel dashboard
Go to Bitcoin app
Click Settings
Click Advanced
Find the section called "Custom bitcoin.conf overrides"
Paste in the following in the box provide and click "Save changes"

reindex=1

dbcache=5000

Your Node should restart and start syncing the Blockchain

To remove later: Simply delete the lines from this box and save.

This will remove them from the config file.

Method B: Command Line

# SSH into Umbrel

ssh umbrel@umbrel.local

# Edit the bitcoin.conf file directly

nano ~/umbrel/app-data/bitcoin/data/bitcoin/bitcoin.conf

# Find and change the lines in the config file to the following:

reindex=1

dbcache=5000

Important:

NO leading dash (-) in the config file
Use = or just the option name alone

For Pi 5 with 8GB RAM, dbcache=5000 is optimal

3. Restart Bitcoin

Save config and restart the Bitcoin app. It will begin reindexing automatically.

4. Wait

Expected time: 12-24 hours on Pi 5 with good storage
With default cache: Could take 1-3 days
Progress will show in the Bitcoin app logs

5. Remove Reindex Flag After Completion

Once reindexing finishes successfully, remove the reindex=1 line from your config (keep the dbcache=5000 line).

Configuration Reference

Optimal Bitcoin Config for Pi 5 (8GB RAM)

dbcache=5000 # Add other settings below as needed

If You Get Errors

Error: parse error... options in configuration file must be specified without leading -
Fix: Remove the - from -reindex → use reindex=1

Error: Prune mode is incompatible with -reindex-chainstate
Fix: Use full reindex=1 instead of reindex-chainstate=1

Prevention Tips

Common Causes of Corruption:

Unstable power supply - Use a quality power adapter
Bad SD card/storage - Consider upgrading to external SSD if using SD card
Storage full - Ensure you have 600GB+ free space
Sudden shutdowns - Always shut down properly

Best Practices:

Use an external SSD instead of SD card for blockchain data
Use a UPS or quality power supply
Monitor disk health regularly
Keep 100GB+ buffer of free space (This is especaily important if using a 1TB drive)

Hardware Specs Used

Device: Raspberry Pi 5
RAM: 8GB
Platform: Umbrel
Node Type: Pruned mode