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# Substrate Node Template
A fresh [Substrate](https://substrate.io/) node, ready for hacking :rocket:
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A standalone version of this template is available for each release of Polkadot
in the [Substrate Developer Hub Parachain
Template](https://github.com/substrate-developer-hub/substrate-parachain-template/)
repository. The parachain template is generated directly at each Polkadot
release branch from the [Node Template in
Substrate](https://github.com/paritytech/substrate/tree/master/bin/node-template)
upstream

It is usually best to use the stand-alone version to start a new project. All
bugs, suggestions, and feature requests should be made upstream in the
[Substrate](https://github.com/paritytech/substrate/tree/master/bin/node-template)
repository.
## Getting Started
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Depending on your operating system and Rust version, there might be additional
packages required to compile this template. Check the
[Install](https://docs.substrate.io/install/) instructions for your platform for
the most common dependencies. Alternatively, you can use one of the [alternative
installation](#alternatives-installations) options.
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### Build

Use the following command to build the node without launching it:
cargo build --release
### Embedded Docs
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After you build the project, you can use the following command to explore its
parameters and subcommands:
```sh
./target/release/node-template -h
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You can generate and view the [Rust
Docs](https://doc.rust-lang.org/cargo/commands/cargo-doc.html) for this template
with this command:
```sh
cargo +nightly doc --open
```

### Single-Node Development Chain
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The following command starts a single-node development chain that doesn't
persist state:
```sh
./target/release/node-template --dev
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```
To purge the development chain's state, run the following command:
```sh
./target/release/node-template purge-chain --dev
To start the development chain with detailed logging, run the following command:
```sh
RUST_BACKTRACE=1 ./target/release/node-template -ldebug --dev
Development chains:

- Maintain state in a `tmp` folder while the node is running.
- Use the **Alice** and **Bob** accounts as default validator authorities.
- Use the **Alice** account as the default `sudo` account.
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- Are preconfigured with a genesis state (`/node/src/chain_spec.rs`) that
  includes several prefunded development accounts.
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To persist chain state between runs, specify a base path by running a command
similar to the following:
// Create a folder to use as the db base path
$ mkdir my-chain-state

// Use of that folder to store the chain state
$ ./target/release/node-template --dev --base-path ./my-chain-state/

// Check the folder structure created inside the base path after running the chain
$ ls ./my-chain-state
chains
$ ls ./my-chain-state/chains/
dev
$ ls ./my-chain-state/chains/dev
db keystore network
```
### Connect with Polkadot-JS Apps Front-End
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After you start the node template locally, you can interact with it using the
hosted version of the [Polkadot/Substrate
Portal](https://polkadot.js.org/apps/#/explorer?rpc=ws://localhost:9944)
front-end by connecting to the local node endpoint. A hosted version is also
available on [IPFS (redirect) here](https://dotapps.io/) or [IPNS (direct)
here](ipns://dotapps.io/?rpc=ws%3A%2F%2F127.0.0.1%3A9944#/explorer). You can
also find the source code and instructions for hosting your own instance on the
[`polkadot-js/apps`](https://github.com/polkadot-js/apps) repository.
### Multi-Node Local Testnet

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If you want to see the multi-node consensus algorithm in action, see [Simulate a
network](https://docs.substrate.io/tutorials/build-a-blockchain/simulate-network/).
## Template Structure

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A Substrate project such as this consists of a number of components that are
spread across a few directories.
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A blockchain node is an application that allows users to participate in a
blockchain network. Substrate-based blockchain nodes expose a number of
capabilities:

- Networking: Substrate nodes use the [`libp2p`](https://libp2p.io/) networking
  stack to allow the nodes in the network to communicate with one another.
- Consensus: Blockchains must have a way to come to
  [consensus](https://docs.substrate.io/fundamentals/consensus/) on the state of
  the network. Substrate makes it possible to supply custom consensus engines
  and also ships with several consensus mechanisms that have been built on top
  of [Web3 Foundation
  research](https://research.web3.foundation/en/latest/polkadot/NPoS/index.html).
- RPC Server: A remote procedure call (RPC) server is used to interact with
  Substrate nodes.

There are several files in the `node` directory. Take special note of the
following:

- [`chain_spec.rs`](./node/src/chain_spec.rs): A [chain
  specification](https://docs.substrate.io/build/chain-spec/) is a source code
  file that defines a Substrate chain's initial (genesis) state. Chain
  specifications are useful for development and testing, and critical when
  architecting the launch of a production chain. Take note of the
  `development_config` and `testnet_genesis` functions,. These functions are
  used to define the genesis state for the local development chain
  configuration. These functions identify some [well-known
  accounts](https://docs.substrate.io/reference/command-line-tools/subkey/) and
  use them to configure the blockchain's initial state.
- [`service.rs`](./node/src/service.rs): This file defines the node
  implementation. Take note of the libraries that this file imports and the
  names of the functions it invokes. In particular, there are references to
  consensus-related topics, such as the [block finalization and
  forks](https://docs.substrate.io/fundamentals/consensus/#finalization-and-forks)
  and other [consensus
  mechanisms](https://docs.substrate.io/fundamentals/consensus/#default-consensus-models)
  such as Aura for block authoring and GRANDPA for finality.
In Substrate, the terms "runtime" and "state transition function" are analogous.
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Both terms refer to the core logic of the blockchain that is responsible for
validating blocks and executing the state changes they define. The Substrate
project in this repository uses
[FRAME](https://docs.substrate.io/learn/runtime-development/#frame) to construct
a blockchain runtime. FRAME allows runtime developers to declare domain-specific
logic in modules called "pallets". At the heart of FRAME is a helpful [macro
language](https://docs.substrate.io/reference/frame-macros/) that makes it easy
to create pallets and flexibly compose them to create blockchains that can
address [a variety of needs](https://substrate.io/ecosystem/projects/).

Review the [FRAME runtime implementation](./runtime/src/lib.rs) included in this
template and note the following:

- This file configures several pallets to include in the runtime. Each pallet
  configuration is defined by a code block that begins with `impl
  $PALLET_NAME::Config for Runtime`.
- The pallets are composed into a single runtime by way of the
  [`construct_runtime!`](https://paritytech.github.io/substrate/master/frame_support/macro.construct_runtime.html)
  macro, which is part of the [core FRAME pallet
  library](https://docs.substrate.io/reference/frame-pallets/#system-pallets).
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The runtime in this project is constructed using many FRAME pallets that ship
with [the Substrate
repository](https://github.com/paritytech/substrate/tree/master/frame) and a
template pallet that is [defined in the
`pallets`](./pallets/template/src/lib.rs) directory.
A FRAME pallet is comprised of a number of blockchain primitives, including:
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- Storage: FRAME defines a rich set of powerful [storage
  abstractions](https://docs.substrate.io/build/runtime-storage/) that makes it
  easy to use Substrate's efficient key-value database to manage the evolving
  state of a blockchain.
- Dispatchables: FRAME pallets define special types of functions that can be
  invoked (dispatched) from outside of the runtime in order to update its state.
- Events: Substrate uses
  [events](https://docs.substrate.io/build/events-and-errors/) to notify users
  of significant state changes.
- Errors: When a dispatchable fails, it returns an error.
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Each pallet has its own `Config` trait which serves as a configuration interface
to generically define the types and parameters it depends on.

## Alternatives Installations

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Instead of installing dependencies and building this source directly, consider
the following alternatives.
### Nix
Install [nix](https://nixos.org/) and
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[nix-direnv](https://github.com/nix-community/nix-direnv) for a fully
plug-and-play experience for setting up the development environment. To get all
the correct dependencies, activate direnv `direnv allow`.
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Please follow the [Substrate Docker instructions
here](https://github.com/paritytech/substrate/blob/master/docker/README.md) to
build the Docker container with the Substrate Node Template binary.