Topic: [Guide] C-Lightning backup guide - page 2. (Read 554 times)

Edit (08/22/2022): The guide has been updated for Core Lightning v0.11.2. It switched from backup plugin to new built-in backup functionality.

For completeness sake, since I already have a topic where I walk through my main node's setup, I am creating this separate guide for backing it up.
I generally follow the official guides, with a few tweaks here and there where I think makes sense. This one here, is based on https://lightning.readthedocs.io/BACKUP.html#sqlite3-wallet-main-backup-and-remote-nfs-mount.

It's worth noting depending on your hardware, it can be trivial to setup the system from the get-go to run on a RAID-0 array, which would mean a constantly up-to-date mirror of your boot drive, but this would be out of the scope of this little guide.

Part 1: hsm_secret backup.
The hsm_secret needs to be backed up once, e.g. on paper, best even multiple copies. Think of it as a seed word backup. It secures the on-chain balance, but we will need Part 2 to always have an up-to-date backup of our channels' states.

[1] Switch to unprivileged bitcoin user and extract the hsm_secret. By using this command, it will open in the text editor and not be saved to your history for better security. It is essential to now write down the hex data on a non-digital medium and afterwards closing vim without saving the file. Do so by opening vim's command prompt (colon), followed by q!, so the whole command will look like :q!↵.

Part 2: Automatic channel state backups

[1] Choose a location for your backup. It makes 0 sense to use a location on the same drive, so it either has to be an external drive (USB / LAN share) or a remote network share. Setting this up is again outside the scope of this guide. Let's assume the location is /mnt/share/lnbackup.

[2] Stop the node and go back into bitcoin user.

[3] Open up the Lightningd configuration file.

[4] Add the following line at the very bottom.
make sure to set the correct path for your (network) share and call it like the original file, i.e. lightningd.sqlite3.

[5] Now we can start up C-Lightning again!

[6] If you get no errors starting up the service or anything, you're good! For good measure, you could send yourself some sats from a mobile wallet, restart the service with sudo service lightningd restart and even restore the node from the backup, then check if everything's fine.