Fork off substrate

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.

Usage

1. Clone this repository and install dependencies

   git clone https://github.com/maxsam4/fork-off-substrate.git
   cd fork-off-substrate
   npm i

2. Create a folder called data inside the top folder (fork-off-substrate).

   mkdir data

3. Copy the executable/binary of your substrate based node inside the data folder and rename it to binary.

4. 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.

5. 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.

6. Either run a full node for your blockchain locally(Recommended) or have an external endpoint handy.

7. Run the script

   • If using a local node, simply run the script using

     npm start -- --chain <desired_chain>

   • If 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 start -- --chain <desired_chain>

   • You can also specify a desired block to scrape data from using --block <block_hash>. It may be necessary to pull this from an archive node if the block is old.

8. You should have the genesis file for the forked chain inside the data folder. It will be called fork.json.

9. You can now run a new chain using this genesis file

   NOTE: most necessary tweaks are handled by the script, but for Moonbeam or Moonriver it will be necessary to manually replace an existing collator with alices' address (0xf24FF3a9CF04c71Dbc94D0b566f7A27B94566cac).

   ./binary --chain fork.json --alice --sealing 1000

Read more

If you would like to understand how this script works, please read this blog post

Credits

This script is based on a script shared in the substrate riot channel