### Understand the alert

The `geth_chainhead_diff_between_header_block` alert is generated by the Netdata Agent when monitoring an Ethereum node using the Geth client. The alert is triggered when there is a significant difference between the chain head header and the actual block number. This indicates that your Ethereum node is out of sync with the rest of the network, and you may experience issues when trying to interact with the blockchain.

### Troubleshoot the alert

1. **Check the sync status of your Ethereum node**: To determine the current sync status of your Ethereum node, execute the following command in the Geth console:

   ```
   eth.syncing
   ```

   If your node is syncing, you'll see information about the syncing progress. If it's not syncing, the command will return `false`.

2. **Restart Geth**: If your node is not syncing, try restarting Geth with the appropriate command for your operating system. For example:

   ```
   sudo systemctl restart geth
   ```

   If Geth isn't running as a system service, you may need to restart it manually. Ensure you're using the correct command-line flags and options.

3. **Check Geth logs**: Inspect the Geth logs for any issues or errors that may provide insight into the problem. You can find the logs in the default log directory or use the `--log-dir` flag to specify a custom log directory. To view the logs in real-time, run:

   ```
   tail -f /path/to/your/log/directory/geth.log
   ```

4. **Ensure your system time is accurate**: An incorrect system time can cause syncing issues. Make sure your system clock is accurate and synchronized with an NTP server:

   ```
   sudo ntpdate -s time.nist.gov
   ```

5. **Upgrade Geth**: Ensure you are running the latest version of Geth. Upgrading to the latest version can resolve issues and improve synchronization. You can find the latest release on the [Geth GitHub repository](https://github.com/ethereum/go-ethereum/releases).

6. **Check your network connection**: Verify that your node has a stable and reliable network connection. If you're on a shared network, consider increasing the bandwidth or moving the node to a dedicated network.

### Useful resources

1. [Geth Documentation](https://geth.ethereum.org/docs/)
2. [Ethereum Stack Exchange](https://ethereum.stackexchange.com/)
3. [Netdata Ethereum Monitoring Guide](https://blog.netdata.cloud/how-to-monitor-the-geth-node-in-under-5-minutes/)
4. [Geth GitHub Repository](https://github.com/ethereum/go-ethereum)
