@ -3,7 +3,7 @@
## Index
* [Installation ](#installation )
* [Overview](# overview)
* [Command overview](#command- overview)
* [Commands ](#commands )
+ [chanbackup ](#chanbackup )
+ [compactdb ](#compactdb )
@ -21,27 +21,175 @@
+ [walletinfo ](#walletinfo )
This tool provides helper functions that can be used to rescue funds locked in
`lnd` channels in case `lnd` itself cannot run properly any more.
`lnd` channels in case `lnd` itself cannot run properly anymore.
**WARNING**: This tool was specifically built for a certain rescue operation and
might not be well-suited for your use case. Or not all edge cases for your needs
are coded properly. Please look at the code to understand what it does before
you use it for anything serious.
**WARNING 2**: This tool will query public block explorer APIs for some of the
**WARNING 2**: This tool will query public block explorer APIs for some
commands, your privacy might not be preserved. Use at your own risk or supply
a private API URL with `--apiurl` .
## Installation
To install this tool, make sure you have `go 1.13.x` (or later) and `make`
installed and run the following command:
installed and run the following commands :
```bash
git clone https://github.com/guggero/chantools.git
cd chantools
make install
```
## Overview
## Channel recovery scenario
The following flow chart shows the main recovery scenario this tool was built
for. This scenario assumes that you do have access to the crashed node's seed,
`channel.backup` file and some state of a `channel.db` file (perhaps from a
file based backup or the recovered file from the crashed node).
**Explanation:**
1. **Node crashed** : For some reason your `lnd` node crashed and isn't starting
anymore. If you get errors similar to
[this ](https://github.com/lightningnetwork/lnd/issues/4449 ),
[this ](https://github.com/lightningnetwork/lnd/issues/3473 ) or
[this ](https://github.com/lightningnetwork/lnd/issues/4102 ), it is possible
that a simple compaction (a full copy in safe mode) can solve your problem.
See [`chantools compactdb` ](#compactdb ).
< br / > < br / >
If that doesn't work and you need to continue the recovery, make sure you can
at least extract the `channel.backup` file and if somehow possible any version
of the `channel.db` from the node.
< br / > < br / >
Whatever you do, do **never, ever** replace your `channel.db` file with an old
version (from a file based backup) and start your node that way. [Read this
explanation why that can lead to loss of funds.](https://github.com/lightningnetwork/lnd/blob/master/docs/safety.md#file-based-backups)
2. **Rescue on-chain balance** : To start the recovery process, we are going to
re-create the node from scratch. To make sure we don't overwrite any old data
in the process, make sure the old data directory of your node (usually `.lnd`
in the user's home directory) is safely moved away (or the whole folder
renamed) before continuing.
< br / >
To start the on-chain recovery, [follow the sub step "Starting On-Chain
Recovery" of this guide](https://github.com/lightningnetwork/lnd/blob/master/docs/recovery.md#starting-on-chain-recovery).
Don't follow the whole guide, only this single chapter!
< br / > < br / >
This step is completed once the `lncli getinfo` command shows both
`"synced_to_chain": true` and `"synced_to_graph": true` which can take several
hours depending on the speed of your hardware. **Do not be alarmed** that the
`lncli getinfo` command shows 0 channels. This is normal as we haven't started
the off-chain recovery yet.
3. **Recover channels using SCB** : Now that the node is fully synced, we can try
to recover the channels using the [Static Channel Backups (SCB) ](https://github.com/lightningnetwork/lnd/blob/master/docs/safety.md#static-channel-backups-scbs ).
For this, you need a file called `channel.backup` . Simply run the command
`lncli restorechanbackup --multi_file <path-to-your-channel.backup>` . **This
will take a while!**. The command itself can take several minutes to complete,
depending on the number of channels. The recovery can easily take a day or
two as a lot of chain rescanning needs to happen. It is recommended to wait at
least one full day. You can watch the progress with the `lncli pendingchannels`
command. If the list is empty, congratulations, you've recovered all channels!
If the list stays un-changed for several hours, it means not all channels
could be restored using this method.
[One explanation can be found here. ](https://github.com/lightningnetwork/lnd/blob/master/docs/safety.md#zombie-channels )
4. **Install chantools** : To try to recover the remaining channels, we are going
to use `chantools` . Simply [follow the installation instructions. ](#installation )
The recovery can only be continued if you have access to some version of the
crashed node's `channel.db` . This could be the latest state as recovered from
the crashed file system, or a version from a regular file based backup. If you
do not have any version of a channel DB, `chantools` won't be able to help
with the recovery. See step 11 for some possible manual steps.
5. **Create copy of channel DB** : To make sure we can read the channel DB, we
are going to create a copy in safe mode (called compaction). Simply run
< br / > < br / >
`chantools compactdb --sourcedb <recovered-channel.db> --destdb ./results/compacted.db`
< br / > < br / >
We are going to assume that the compacted copy of the channel DB is located in
`./results/compacted.db` in the following commands.
6. **chantools summary** : First, `chantools` needs to find out the state of each
channel on chain. For this, a blockchain API (by default [blockstream.info ](https://blockstream.info ))
is queried. The result will be written to a file called
`./results/summary-yyyy-mm-dd.json` . This result file will be needed for the
next command.
< br / > < br / >
`chantools --fromchanneldb ./results/compacted.db summary`
7. **chantools rescueclosed** : It is possible that by now the remote peers have
force-closed some of the remaining channels. What we now do is try to find the
private keys to sweep our balance of those channels. For this we need a shared
secret which is called the `commit_point` and is changed whenever a channel is
updated. We do have the latest known version of this point in the channel DB.
The following command tries to find all private keys for channels that have
been closed by the other party. The command needs to know what channels it is
operating on, so we have to supply the `summary-yyy-mm-dd.json` created by the
previous command:
< br / > < br / >
`chantools --fromsummary ./results/<summary-file-created-in-last-step>.json rescueclosed --channeldb ./results/compacted.db`
< br / > < br / >
This will create a new file called `./results/rescueclosed-yyyy-mm-dd.json`
which will contain any found private keys and will also be needed for the next
command. Use `bitcoind` or Electrum Wallet to sweep all of the private keys.
8. **chantools forceclose** : This command will now close all channels that
`chantools` thinks are still open. This is achieved by publishing the latest
known channel state of the `channel.db` file.
< br / > **Please read the full warning text of the
[`forceclose` command below ](#forceclose ) as this command can put
your funds at risk** if the state in the channel DB is not the most recent
one. This command should only be executed for channels where the remote peer
is not online anymore.
< br / > < br / >
`chantools --fromsummary ./results/<rescueclosed-file-created-in-last-step>.json forceclose --channeldb ./results/compacted.db --publish`
< br / > < br / >
This will create a new file called `./results/forceclose-yyyy-mm-dd.json`
which will be needed for the next command.
9. **Wait for timelocks** : The previous command closed the remaining open
channels by publishing your node's state of the channel. By design of the
Lightning Network, you now have to wait until the channel funds belonging to
you are not time locked any longer. Depending on the size of the channel, you
have to wait for somewhere between 144 and 2000 confirmations of the
force-close transactions. Only continue with the next step after the channel
with the highest `csv_timeout` has reached that many confirmations of its
closing transaction.
10. **chantools sweeptimelock** : Once all force-close transactions have reached
the number of transactions as the `csv_timeout` in the JSON demands, these
time locked funds can now be swept. Use the following command to sweep all the
channel funds to an address of your wallet:
< br / > < br / >
`chantools --fromsummary ./results/<forceclose-file-created-in-last-step>.json sweeptimelock --publish --sweepaddr <bech32-address-from-your-wallet>`
11. **Manual intervention necessary** : You got to this step because you either
don't have a `channel.db` file or because `chantools` couldn't rescue all your
node's channels. There are a few things you can try manually that have some
chance of working:
- Make sure you can connect to all nodes when restoring from SCB: It happens
all the time that nodes change their IP addresses. When restoring from a
static channel backup, your node tries to connect to the node using the IP
address encoded in the backup file. If the address changed, the SCB restore
process doesn't work. You can use block explorers like [1ml.com ](https://1ml.com )
to try to find an IP address that is up-to-date. Just run
`lncli connect <node-pubkey>@<updated-ip-address>:<port>` in the recovered
`lnd` node from step 3 and wait a few hours to see if the channel is now
being force closed by the remote node.
- Find out who the node belongs to: Maybe you opened the channel with someone
you know. Or maybe their node alias contains some information about who the
node belongs to. If you can find out who operates the remote node, you can
ask them to force-close the channel from your end. If the channel was opened
with the `option_static_remote_key` , (`lnd v0.8.0` and later), the funds can
be swept by your node.
## Command overview
```text
Usage:
Oliver Gugger
4 years ago
