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https://github.com/maxsam4/fork-off-substrate

This script allows bootstrapping a new substrate chain with the current state of a live chain
https://github.com/maxsam4/fork-off-substrate

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This script allows bootstrapping a new substrate chain with the current state of a live chain

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# 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



    ```bash

    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`).



    ```bash

    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](https://github.com/paritytech/polkadot/releases).



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": {  } }`. 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



        ```bash

        npm start

        ```



    * If you are using an external/non-default endpoint, you need to provide it to the script via the `HTTP_RPC_ENDPOINT` environment variable



        ```bash

        HTTP_RPC_ENDPOINT=https://example.com npm start

        ```



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



    ```bash

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

    ```



## Configuration



The 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` | 



## Read more



If you would like to understand how this script works, please read this [blog post](https://mudit.blog/fork-substrate-blockchain/)



## Using Docker



### Build the image



    docker build -t fork-off-substrate .



### Run



    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



## Credits



This script is based on [a script shared in the substrate riot channel](https://hackmd.io/mGgNZX0VT4S0UTaq89-_SQ)