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This script allows bootstrapping a new substrate chain with the current state of a live chain. Using this, you can create a fork of Polkadot, Kusama and other substrate chain for development purposes.
Clone this repository and install dependencies
git clone https://github.com/maxsam4/fork-off-substrate.git
cd fork-off-substrate
npm iCreate a folder called data inside the top folder (fork-off-substrate).
mkdir dataCopy the executable/binary of your substrate based node inside the data folder and rename it to binary.
Copy the runtime WASM blob of your substrate based blockchain to the data folder and rename it to runtime.wasm. To get the WASM blob, compile your blockchain and look for ./target/release/wbuild/runtime/runtime.compact.wasm. If you are forking Polkadot/Kusama/Westend, you can download the WASM blobs from Polkadot's release page.
If your substrate chain uses additional custom types than what are available in polkadot.js, define them in a JSON file of format { "types": { <YOUR_TYPES> } }. Copy the file to the data folder and rename it to schema.json.
Either run a full node for your blockchain locally(Recommended) or have an external endpoint handy.
Run the script
If using a local node, simply run the script using
npm startIf you are using an external/non-default endpoint, you need to provide it to the script via the HTTP_RPC_ENDPOINT environment variable
HTTP_RPC_ENDPOINT=https://example.com npm startYou should have the genesis file for the forked chain inside the data folder. It will be called fork.json.
You can now run a new chain using this genesis file
./binary --chain fork.json --aliceThe script can be tweaked and configured using various environment variables -
| Environment Variable | Effects | Default value |
|---|---|---|
| HTTP_RPC_ENDPOINT | HTTP RPC endpoint that should be used to query state | http://localhost:9933 |
| FORK_CHUNKS_LEVEL | Determines how many chunks to split the RPC download in. Effect is exponential, recommended value for most is 1. You can try 0 for small chains and 2 for large chains for potential speed improvements | 1 |
| ORIG_CHAIN | Chain to use as the original chain. | $default_of_the_binary |
| FORK_CHAIN | Chain to use as base for the forked chain. | dev |
| ALICE | If set, the script will replace the chain's sudo account with //Alice | NULL |
| QUICK_MODE | If set, it parallelizes the data download from the RPC endpoint | NULL |
If you would like to understand how this script works, please read this blog post
docker build -t fork-off-substrate .
BINARY=/full/path/to/your/linux/binary
HTTP_RPC_ENDPOINT=http://localhost:9933
docker run --rm -it \
-e HTTP_RPC_ENDPOINT=$HTTP_RPC_ENDPOINT \
-v "$BINARY":/data/binary
fork-off-substrate
This script is based on a script shared in the substrate riot channel
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