Backup your wallet

In Lightning, since you are the only one storing all your financial information, you cannot recover this financial information from anywhere else.This means that on Lightning, you have to responsibly back up your financial information yourself, using various processes and automation.

The discussion below assumes that you know the location of your $LIGHTNINGDIR, and you know the directory structure within. By default your $LIGHTNINGDIR will be ~/.lightning/${COIN}. For example, if you are running --mainnet, $LIGHTNINGDIR will be ~/.lightning/bitcoin.

Backup

Core Lightning has an internal bitcoin wallet and you can backup three main components from the wallet:

• HSM Secret: On-chain funds are backed up via the HD wallet seed, stored in byte-form as hsm_secret
• Static Channel: Lightning channel states to recover are stored in a file named emergency.recover
• Database: Detailed information for funds locked in channels are stored in the database

HSM Secret Backup

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Who should do this:

Everyone.

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Recovery of the hsm_secret is sufficient to recover any onchain funds.

Recovery of the hsm_secret is necessary, but insufficient, to recover any in-channel funds.

The hsm_secret is highly confidential, and its loss could lead to the theft of your funds. Therefore, it is crucial to ensure that
it is kept in a secure location.

The hsm_secret is created when you first create the node, and does not change. Thus, a one-time backup of hsm_secret is sufficient.
It should be noted down a few times on a piece of paper, in either hexadecimal or codex32 format, as described below:

Hex Format

The secret is just 32 bytes, and can be converted into hexadecimal digits like below:

cd $LIGHTNINGDIR
xxd hsm_secret

To convert above hex back into the binary hsm_secret (32 bytes format) for recovery, you can re-enter the hexdump into a text file and use xxd:

cat > hsm_secret_hex.txt <<HEX
00: 30cc f221 94e1 7f01 cd54 d68c a1ba f124
10: e1f3 1d45 d904 823c 77b7 1e18 fd93 1676
HEX
xxd -r hsm_secret_hex.txt > hsm_secret
chmod 0400 hsm_secret

Codex32 Format

Run tools/hsmtool getcodexsecret <hsm/secret/path> <id> to get the hsm_secret in codex32 format.

Example tools/hsmtool getcodexsecret ~/.lightning/bitcoin/hsm_secret adt0.

hsm/secret/path in the above command is $LIGHTNINGDIR/hsm_secret, and
id is any 4 character string used to identify this secret. It cannot contain i, o, or b, but can contain all digits except 1.

Click here to learn more about other cool hsm methods.

Static Channel Backup

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Who should do this:

Those who already have at least one channel.

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It's important to note that static channel recovery requires cooperation with peers and should only be used as a last resort to retrieve coins that are stuck in a channel.

This feature allows users to get the static channel backup in the form of emergency.recover file located in the $LIGHTNINGDIR.

This file gets updated each time you open a new channel. Therefore, it's recommended that you backup this file whenever a new channel is opened.

Database Backup

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Who should do this:

Casual users.

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Snapshot-style backups of the lightningd database is discouraged, as any loss of state may result in permanent loss of funds.

See the penalty mechanism for more information on why any amount of state-loss results in fund loss.

lightningd also stores detailed information of funds locked in Lightning Network channels in a database. This database is required for on-going channel updates as well as channel closure. There is no single-seed backup for funds locked in channels.

Real-time database replication is the recommended approach to backing up node data. Tools for replication are currently in active development, using the db write plugin hook.

Click here to learn more about advanced DB backup methods.