Quickstart: Launch an Orbit chain
This quickstart is for developers who want to launch their own Arbitrum Orbit chain using the Orbit chain deployment portal.
This quickstart is intended for development purposes only and is not suitable for deploying production-grade mainnet chains.
By the end of this quickstart, you'll have a local devnet chain that hosts EVM-compatible smart contracts. Your chain will process transactions locally while settling to the public Arbitrum Sepolia testnet. Familiarity with Ethereum, Ethereum's testnets, and Arbitrum is expected.
If you're looking for a conceptual introduction to Orbit chains, see the Gentle introduction to Orbit chains.
Prerequisites
- Docker
- A browser-based Ethereum wallet (like MetaMask)
- At least 1.2 testnet ETH (for custom gas token chains, 0.8 ETH and 0.4 native tokens)
Step 1: Acquire Arbitrum Testnet $ETH (and the native token for Orbit chains with custom gas tokens)
You'll need at least 1.2 testnet $ETH for regular Orbit chains or 0.8 $ETH plus 0.4 of your desired native token for Orbit chains with a custom gas token. The funds are needed to cover the cost of deploying your Orbit chain's base contracts to its base chain (Arbitrum Sepolia).
At the time of this quickstart's writing, the easiest way to acquire $ETH is to bridge testnet $ETH from Ethereum's L1 Sepolia network to Arbitrum Sepolia L2 testnet:
- Use an L1 testnet $ETH faucet like sepoliafaucet.com to acquire some testnet $ETH on an L1 testnet.
- Bridge your L1 testnet $ETH into Arbitrum L2 using the Arbitrum bridge.
Step 2: Choose your chain type: AnyTrust or Rollup
Arbitrum Rollup is an Optimistic Rollup protocol; it's trustless and permissionless. These properties are achieved by requiring all chain data to be posted on Ethereum's "Layer 1" (L1) chain. This means the availability of this data follows directly from the security properties of Ethereum itself, and, in turn, that any party can participate in validating the chain and ensuring its safety.
By contrast, Arbitrum AnyTrust introduces a trust assumption in exchange for lower fees. Instead of requiring all Arbitrum nodes to have access to the data of every L2 transaction in the Arbitrum chain's inbox, AnyTrust relies on an external Data Availability Committee to store data and provide it on demand, reducing the costs of batching and posting all L2 transaction data to L1. Visit our FAQ docs to learn more.
We generally recommend using Rollup chains for use-cases that demand the highest level of security (like decentralized exchanges and other DeFi dApps). AnyTrust chains are suitable for use-cases that require lower fees and generate lots of transactions (like gaming and social dApps).
Step 3: Configure your Orbit chain's deployment
Visit the Orbit chain deployment portal. You'll be prompted to connect your wallet. You may be prompted to add the Arbitrum Sepolia network to your wallet and/or to switch your wallet to this network; approve this.
The deployment portal will then display a form that looks like this:
The below table provides a brief description of each of these configuration parameters. We recommend sticking to the defaults; to learn more about customizing your Orbit chain's deployment configuration, visit How (and when) to customize your Orbit chain's deployment config:
| Parameter | Description |
|---|---|
| Chain ID | A unique integer identifier that represents your chain's network. Your Chain ID can be submitted to chain indexes like Chainlist.org. For devnets, this is randomly generated for each deployment - don't worry about it for now. |
| Chain name | A human-readable way to distinguish your Orbit chain from other Orbit chains. Users, developers and the wider community will refer to your chain by your Chain name and/or your Chain ID. |
| Challenge period (blocks) | The amount of time that your Orbit chain's nodes have to dispute the current state of the chain before it's confirmed (and ultimately finalized) on the underlying L2 chain (e.g. Arbitrum Sepolia). Note that this refers to the number of blocks on the underlying L1 chain (e.g. Ethereum's Sepolia chain). |
| Stake token | The token that your chain's validators must stake in order to participate in your chain. This is hardcoded to $ETH for now, but future versions of Orbit chains will let you specify an arbitrary ERC-20 token contract here. |
| Base stake | The amount of your configured Stake token that your chain's validators must stake in order to participate in your chain. Should be greater than 0. |
| Owner | The administrative Ethereum address that will deploy, own, and update your chain's base contracts. This will default to your connected wallet's address. This needs to be a standard Ethereum wallet account - an EOA, not a contract address. Note that you'll have to specify this wallet's private key within a local JSON file later. |
| Gas token | The address of the ERC-20 token on the parent chain that is intended to be used as the native gas token on the Orbit chain. This token must already be deployed natively on the parent chain and is bridged to the Orbit chain during chain deployment. This feature is only supported on AnyTrust chains currently, and more information around token restrictions can be found here. |
Step 4: Configure your chain's validator(s)
You should see a Configure Validators section appear, with a form that looks like this:
The first input field is an integer value that determines the number of validators that will support your initial deployment. Subsequent fields allow you to specify each of these validators' addresses.
The first validator address is randomly generated and can't be changed. Its private key will be automatically generated and stored within one of the JSON configuration files that will be generated in a moment.
Your chain's validators are responsible for validating the integrity of transactions and posting assertions of the current state of your Orbit chain to its base chain. In production scenarios, your Orbit chain would likely be hosted by a network of validator nodes working together. For your local Orbit chain, you can stick to the auto-generated single validator address.
Each of the validator addresses specified in this step will be added to an allow-list in one of your chain's base contracts, allowing them each to stake and validate transactions submitted to your Orbit chain.
When we say "base contracts" and "base chain", we're referring to your Orbit chain's L2 contracts and the L2 chain that they're deployed to, respectively. We'll use these terms throughout the rest of this guide.
Once your validator addresses are configured, click Next to proceed the next step: batch poster configuration.
Step 5: Configure your chain's batch poster
You should see a Configure Batch Poster section appear, with a form that looks like this:
Your batch poster address is responsible for posting batches of transactions from your Orbit chain to its base contracts on its base chain. An address will automatically be generated for you; its private key will be automatically generated and stored within one of the JSON configuration files that will be generated in a moment.
Once your batch poster address is configured, click Next to proceed to the next step: review & deploy your Orbit chain.
Step 6: Review & Deploy your Orbit chain
Deploy your chain's base contracts to Arbitrum Sepolia
Click the Deploy button located below the config form. Your wallet should prompt you to submit a transaction to the Arbitrum testnet. You'll have to pay a little gas; your wallet may denominate this in $ETH; as long as you see your chosen Arbitrum testnet in the transaction details, this gas fee will be paid in testnet $ETH.
Before proceeding, let's briefly review what just happened:
- You submitted a deployment transaction to an Orbit "factory" smart contract on the Arbitrum testnet, the public L2 chain that your local Orbit chain will settle transactions to.
- This Orbit smart contract then initialized your Orbit chain's base contracts with the values that you specified in the previous step, and deployed these base contracts to the Arbitrum testnet.
Your Orbit chain's base contracts are responsible for facilitating the exchange of information between your chain's node(s) and its base chain's nodes. This includes the batch posting of transactions from your Orbit chain to its base chain, the staking of tokens by your Orbit chain's validators, the challenge mechanism, bridging mechanisms, and more.
Once your transaction is complete, if you deployed an AnyTrust chain, you'll next be asked to configure your keyset. Otherwise, continue to Step 8 to download your chain's configuration files and launch your chain.
Step 7: Configure keyset (AnyTrust chains only)
Skip this step if you're deploying a Rollup chain.
For the Batch Poster to function correctly, it's essential that the keyset corresponding to its current configuration is active within the SequencerInbox contract. The production of the keyset and keyset hash binary blobs is mandatory, which should then be used as inputs for the SetValidKeyset method on the SequencerInbox contract.
The current version of Orbit AnyTrust chains uses a single Data Availability Server and assigns a null value to its private key in order to generate an initial keyset. As part of this transaction process, you'll assign this initial keyset to your recently generated SequencerInbox contract.
Click the Deploy button located below the Deployment Summary. Again, your wallet should prompt you to submit a transaction to the Arbitrum testnet. Gas fees will be handled similarly to the previous transaction.
Once the transaction completes, you'll be directed to the download page to continue your chain deployment.
Step 8: Download your chain's configuration files and launch your chain
You should see two JSON code blocks appear labeled Rollup Config and L3 Config. Use the download buttons at the top right of each code block to save it locally.
- Download Rollup JSON: This will generate
nodeConfig.json, which contains your chain's node configuration. Note that this includes the private keys for your validator (staker) and batch poster, which are used to sign transactions that post RBlocks and batches to your chain's base contracts on L2. - Download L3Config JSON: This will generate
orbitSetupScriptConfig.json, which contains your chain's configuration, including that which supports your Token Bridge contracts.
Step 9: Clone the setup script repository and add your configuration files
- Clone the orbit-setup-script repository:
git clone https://github.com/OffchainLabs/orbit-setup-script.git - Move the
nodeConfig.jsonfile that you downloaded into theconfigdirectory in the root of your clonedorbit-setup-scriptrepository. - Move the
orbitSetupScriptConfig.jsonfile you downloaded into theconfigdirectory in the root of your clonedorbit-setup-scriptrepository. - Install dependencies by running
yarn installfrom the root of theorbit-setup-scriptrepository.
Step 10: Run your chain's node and block explorer
Run Docker, then run docker-compose up -d from the root of the orbit-setup-script repository.
A Nitro node and BlockScout explorer instance will be started. Visit http://localhost/ to access your BlockScout explorer instance - this will allow you to view your chain's transactions and blocks, which can be useful for debugging.
Step 11: Finish setting up your chain
We've provided a Hardhat script that handles the following tasks:
- Fund the batch-poster and validator (staker) accounts on your underlying L2 chain.
- Deposit ETH into your account on the chain using your chain's newly deployed bridge.
- Deploy your Token Bridge contracts on both L2 and local Orbit chains.
- Configure parameters on the chain.
To run this script, issue the following command from the root of the orbit-setup-script repository, replacing OxYourPrivateKey with the private key of the Owner account you used to deploy your chain's contracts, and replacing http://localhost:8449 with the RPC URL of your chain's node.
Using Arbitrum Sepolia:
PRIVATE_KEY="0xYourPrivateKey" L2_RPC_URL="https://sepolia-rollup.arbitrum.io/rpc" L3_RPC_URL="http://localhost:8449" yarn run setup
Congratulations
Your local Orbit chain is now running. You'll see an outputInfo.json file in the main directory of your script folder - this contains more information about your chain, including the addresses of your chain's base contracts.
Appendix A: Logging
Run this command in the root directory of your cloned orbit setup script repo to view your chain's logs:
docker-compose logs -f nitro
Appendix B: Depositing ETH/native token
If you need to deposit more ETH (or native tokens) into your Orbit chain account, run this command on the base directory of the setup script, replacing 0xYourPrivateKey with the private key of the originating account, and <AMOUNT> with the amount to send:
Using Arbitrum Sepolia:
PRIVATE_KEY="0xYourPrivateKey" L2_RPC_URL="https://sepolia-rollup.arbitrum.io/rpc" L3_RPC_URL="http://localhost:8449"
AMOUNT="<AMOUNT>" yarn run deposit
Appendix C: Troubleshooting
- You may see
error getting latest batch countin your node's output logs (from Appendix A). This is usually safe to ignore. It's usually displayed when your Orbit chain's base contract deployment isn't yet finalized on the L1 chain. This finalization can take 15-20 minutes, but don't worry - the deployment doesn't need to be L1-finalized in order for your chain to function properly.