Cumulus ☁️

Cumulus is a Parachain development kit (PDK). It is a set of tools used to create Polkadot compatible Parachains using the Substrate development framework.

You can learn more about Cumulus by reading the Overview

Cumulus clouds are shaped sort of like dots; together they form a system that is intricate, beautiful, and functional.

Getting Started

This tutorial will guide you through the steps needed to launch and connect a Parachain to a Relay Chain using Cumulus.

Step 1: Launch a Relay Chain

Use Polkadot to launch a Relay Chain node. This tutorial uses Rococo, a public testnet specifically for Parachains.

# launch a relay chain node
git clone https://github.com/paritytech/polkadot.git
cd polkadot
git fetch
git checkout rococo-v1
cargo build --release --features=real-overseer

# generate a raw rococo chain-spec
./target/release/polkadot build-spec \
   --chain rococo-local \
   --disable-default-bootnode \
   --raw > rococo-local-cfde.json

# start Alice's node
./target/release/polkadot --chain rococo-local-cfde.json --alice

# start Bob's node (in a separate terminal and port)
./target/release/polkadot --chain rococo-local-cfde.json --bob --port 30334

Step 2: Launch A Parachain

Use Cumulus to launch a Parachain node.

# clone the cumulus repository
git clone https://github.com/paritytech/cumulus
cd cumulus
git fetch
git checkout rococo-v1
cargo build --release -p rococo-collator

# export genesis state
# --parachain-id 200 is an arbitrary number chosen freely. use the same parachain id everywhere
./target/release/rococo-collator export-genesis-state --parachain-id 200 > genesis-state

# export genesis wasm
./target/release/rococo-collator export-genesis-wasm > genesis-wasm

# launch collator node
./target/release/rococo-collator \
   --collator \
   --tmp \
   --parachain-id 200 \
   --port 40335 \
   --ws-port 9946 \
   -- \
   --execution wasm \
   --chain ../polkadot/rococo-local-cfde.json \
   --port 30335

# launch full node
./target/release/rococo-collator \
   --tmp \
   --parachain-id 200 \
   --port 40337 \
   --ws-port 9948 \
   -- \
   --execution wasm \
   --chain ../polkadot/rococo-local-cfde.json 
   --port 30337

Step 3: Register with the Relay Chain

Use Cumulus to register the Parachain. This is normally done in the Polkadot network with auctions, but tutorial uses Sudo.

A transaction registering the Parachain can be submitted from Apps > Sudo > parasSudoWrapper > sudoScheduleParaInitialize with parameters generated in Step 2:

• id: 200
• genesisHead: genesis-state
• validationCode: genesis-wasm
• parachain: Yes

Further Resources

• Cumulus Workshop
• Architectural Overview
• Substrate Developer Hub