How to setup a watchtower

This tutorial will show you how to configure your Electrum daemon as a watchtower for your lightning wallet. It is written for Electrum 4.0.

A watchtower is a separate Electrum process, that runs on another computer. To setup a watchtower, you need to configure an Electrum daemon, and enter its URL in your preferences.

How to configure a watchtower

You want to run your watchtower on a machine that is regularly connected to the internet.

First install Electrum, and add a SSL certificate to your Electrum configuration:

electrum -o setconfig ssl_keyfile /path/to/ssl/privkey.pem
electrum -o setconfig ssl_certfile /path/to/ssl/fullchain.pem

For details see How to add SSL

Second, configure your watchtower with an address, username and password:

electrum setconfig -o run_watchtower true
electrum setconfig -o watchtower_user myusername
electrum setconfig -o watchtower_password mypassword
electrum setconfig -o watchtower_address example.com:12345

Then start the daemon:

electrum daemon -d

The watchtower database contains presigned transactions, and is in ~/.electrum/watchtower_db

Note that the daemon does not need to contain a wallet, nor to have Lightning enabled; the watchtower is only about watching onchain addresses and broadcasting onchain transactions.

If you run Electrum’s Qt GUI on the machine that is configured as a watchtower, you can view the database size and number of transactions per channel if you open the watchtower window:

Configure the watchtower in your client

In your client preferences, tick ‘use a remote watchtower’ and enter the url:

https://myusername:mypassword@example.com:12345