[stable2407] Backport #6646

cumulus/polkadot-omni-node/README.md

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+# Polkadot Omni Node
+
+This is a white labeled implementation based on [`polkadot-omni-node-lib`](https://crates.io/crates/polkadot-omni-node-lib).
+It can be used to start a parachain node from a provided chain spec file. It is only compatible with runtimes that use block
+number `u32` and `Aura` consensus.
+
+## Installation
+
+Download & expose it via `PATH`:
+
+```bash
+# Download and set it on PATH.
+wget https://github.com/paritytech/polkadot-sdk/releases/download/<stable_release_tag>/polkadot-omni-node
+chmod +x polkadot-omni-node
+export PATH="$PATH:`pwd`"
+```
+
+Compile & install via `cargo`:
+
+```bash
+# Assuming ~/.cargo/bin is on the PATH
+cargo install polkadot-omni-node
+```
+
+## Usage
+
+A basic example for an Omni Node run starts from a runtime which implements the [`sp_genesis_builder::GenesisBuilder`](https://docs.rs/sp-genesis-builder/latest/sp_genesis_builder/trait.GenesisBuilder.html).
+The interface mandates the runtime to expose a [`named-preset`](https://docs.rs/staging-chain-spec-builder/latest/staging_chain_spec_builder/#generate-chain-spec-using-runtime-provided-genesis-config-preset).
+
+### 1. Install chain-spec-builder
+
+**Note**: `chain-spec-builder` binary is published on [`crates.io`](https://crates.io) under
+[`staging-chain-spec-builder`](https://crates.io/crates/staging-chain-spec-builder) due to a name conflict.
+Install it with `cargo` like bellow :
+
+```bash
+cargo install staging-chain-spec-builder
+```
+
+### 2. Generate a chain spec
+
+Omni Node expects for the chain spec to contain parachains related fields like `relay_chain` and `para_id`.
+These fields can be introduced by running [`staging-chain-spec-builder`](https://crates.io/crates/staging-chain-spec-builder)
+with additional flags:
+
+```bash
+chain-spec-builder create --relay-chain <relay_chain_id> --para-id <id> -r <runtime.wasm> named-preset <preset_name>
+```
+
+### 3. Run Omni Node
+
+And now with the generated chain spec we can start the node in development mode like so:
+
+```bash
+polkadot-omni-node --dev --chain <chain_spec.json>
+```
+
+## Useful links
+
+* [`Omni Node Polkadot SDK Docs`](https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_docs/reference_docs/omni_node/index.html)
+* [`Chain Spec Genesis Reference Docs`](https://paritytech.github.io/polkadot-sdk/master/polkadot_sdk_docs/reference_docs/chain_spec_genesis/index.html)
+* [`polkadot-parachain-bin`](https://crates.io/crates/polkadot-parachain-bin)
+* [`polkadot-sdk-parachain-template`](https://github.com/paritytech/polkadot-sdk-parachain-template)
+* [`frame-omni-bencher`](https://crates.io/crates/frame-omni-bencher)
+* [`staging-chain-spec-builder`](https://crates.io/crates/staging-chain-spec-builder)