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: