QBFT Consensus Fix: Removing ethash from Genesis

Date: 2025-12-20
Root Cause: Genesis file had both ethash: {} and qbft: {...}, causing Besu to default to ethash (proof-of-work) instead of QBFT

Problem

Besu was not recognizing validators and blocks were not being produced because:

Genesis config had both ethash: {} and qbft: {...}
Besu defaulted to ethash (proof-of-work) consensus instead of QBFT
This caused validators to not be recognized (empty validator set)
No blocks could be produced (ethash requires mining, which isn't configured)

Solution

Removed ethash: {} from the genesis.json config section, keeping only qbft: {...}.

Before:

{
  "config": {
    "clique": null,
    "ethash": {},
    "qbft": {
      "blockperiodseconds": 2,
      "epochlength": 30000,
      "requesttimeoutseconds": 10
    }
  }
}

After:

{
  "config": {
    "clique": null,
    "qbft": {
      "blockperiodseconds": 2,
      "epochlength": 30000,
      "requesttimeoutseconds": 10
    }
  }
}

Results

After deploying the fixed genesis.json:

✅ Validators are now recognized: qbft_getValidatorsByBlockNumber returns 5 validators
✅ QBFT consensus is active (validators list populated)
✅ Services are running correctly

Blocks should now start being produced with a 2-second block period.

Action Taken

Removed ethash: {} from smom-dbis-138-proxmox/config/genesis.json
Deployed updated genesis.json to all nodes (VMIDs 1000-1004, 1500-1503, 2500-2502)
Cleared all databases (to reinitialize with correct genesis)
Restarted all Besu services

Verification

# Validators are now recognized
$ curl -X POST --data '{"jsonrpc":"2.0","method":"qbft_getValidatorsByBlockNumber","params":["latest"],"id":1}' http://localhost:8545
{
  "result": [
    "0x11563e26a70ed3605b80a03081be52aca9e0f141",
    "0x1c25c54bf177ecf9365445706d8b9209e8f1c39b",
    "0x22f37f6faaa353e652a0840f485e71a7e5a89373",
    "0x573ff6d00d2bdc0d9c0c08615dc052db75f82574",
    "0xc4c1aeeb5ab86c6179fc98220b51844b74935446"
  ]
}

Lesson Learned

For QBFT consensus networks, the genesis file should only have the qbft config, not both ethash and qbft. Having both causes Besu to default to ethash, which is incompatible with QBFT validator-based consensus.

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