How to Run a Sequencer Node

Background

The Aztec sequencer node is critical infrastructure responsible for ordering transactions and producing blocks.

When transactions enter the network, the sequencer node bundles them into blocks, checking various constraints such as gas limits, block size, and transaction validity. Before a block can be published, it must be validated by a committee of other sequencer nodes (validators in this context) who re-execute the transactions to verify their correctness. These validators attest to the block's validity by signing it, and once enough attestations are collected (two-thirds of the committee plus one), the sequencer can submit the block to L1.

The archiver component complements this process by maintaining historical chain data. It continuously monitors L1 for new blocks, processes them, and maintains a synchronized view of the chain state. This includes managing contract data, transaction logs, and L1-to-L2 messages, making it essential for network synchronization and data availability.

Prerequisites

Before following this guide, make sure you:

• Have the aztec tool installed
• Are running a Linux or MacOS machine with access to a terminal

Setting Up Your Sequencer

This guide will describe how to setup your sequencer using the aztec start command. For more advanced setups, refer to the Advanced Configuration section below.

The aztec start tool is a one-stop-shop for running your sequencer on any Aztec Network. It assigns default values to several config variables based on a --network flag and launches a docker container running the sequencer software.

To use the aztec start command, you need to obtain the following:

RPCs

• An L1 execution client (for reading transactions and state). It can be specified via the --l1-rpc-urls flag when using aztec start or via the env var ETHEREUM_HOSTS.

• An L1 consensus client (for blobs). It can be specified via the --l1-consensus-host-urls flag when using aztec start or via the env var L1_CONSENSUS_HOST_URLS.

• To reduce load on your consensus endpoint, the Aztec sequencer supports an optional (but recommended) remote server that serves blobs to the client. You can pass your own or use one provided by a trusted party via the --sequencer.blobSinkUrl flag when using aztec start, or via the env var BLOB_SINK_URL.

Ethereum Keys

You will need an Ethereum private key and the corresponding public address. The private key is set via the --sequencer.validatorPrivateKey flag while the public address should be specified via the --sequencer.coinbase flag.

The private key is needed as your validator will post blocks to Ethereum, and the public address will be the recipient of any block rewards.

Networking

You MUST forward your ports. Your router must send UDP and TCP traffic on port 40400 (unless you changed the default) to your IP address on your local network. Failure to do so may result in your sequencer not participating on the p2p network.

As a tip, configure your router to give your MAC address the same IP address every time it does a DHCP refresh.

You also need to grab your external IP address and pass it along to the --p2p.p2pIp when using aztec start.

Sepolia ETH

You'll need Sepolia ETH to cover gas costs. Here are some options:

• Use a PoW faucet like Sepolia PoW Faucet
• Ask in our Discord community (and remember to pay it forward when you can!)

Now Start Your Sequencer

To boot up a sequencer using aztec start, run the following command:

aztec start --network alpha-testnet \
  --l1-rpc-urls https://example.com \
  --l1-consensus-host-urls https://example.com \
  --sequencer.validatorPrivateKey 0xYourPrivateKey \
  --sequencer.coinbase 0xYourAddress
  --p2p.p2pIp 999.99.999.99

tip

For a full overview of all available commands, check out the CLI reference sheet.

tip

If you are unable to determine your public ip. Running the command curl ifconfig.me can retrieve it for you.

Register as a Validator

Once your node is fully synced, you can register as a validator using the add-l1-validator command:

aztec add-l1-validator \
  --network alpha-testnet \
  --l1-rpc-urls https://eth-sepolia.g.example.com/example/your-key \
  --private-key your-private-key \
  --attester your-validator-address \
  --proposer-eoa your-validator-address \
  --staking-asset-handler 0xF739D03e98e23A7B65940848aBA8921fF3bAc4b2 \
  --l1-chain-id 11155111 \

Advanced Configuration

Using Environment Variables

Every flag in the aztec start command corresponds to an environment variable. You can see the variable names by running aztec start --help. A reference is provided here.

For example:

• --l1-rpc-urls maps to ETHEREUM_HOSTS
• --l1-consensus-host-urls maps to L1_CONSENSUS_HOSTS_URLS

You can create a .env file with these variables:

ETHEREUM_HOSTS=https://example.com
L1_CONSENSUS_HOST_URLS=https://example.com
# Add other configuration variables as needed

Then source this file before running your command:

source .env
aztec start --network alpha-testnet --archiver --node --sequencer # other flags...

Using a Docker Compose

If you would like to run in a docker compose, you can use a configuration like the one below:

name: aztec-node
services:
  network_mode: host # Optional, run with host networking
  node:
    image: aztecprotocol/aztec:0.85.0-alpha-testnet.2
    environment:
      ETHEREUM_HOSTS: ""
      L1_CONSENSUS_HOST_URLS: ""
      DATA_DIRECTORY: /data
      VALIDATOR_PRIVATE_KEY: $VALIDATOR_PRIVATE_KEY
      P2P_IP: $P2P_IP
      LOG_LEVEL: debug
    entrypoint: >
      sh -c 'node --no-warnings /usr/src/yarn-project/aztec/dest/bin/index.js start --network alpha-testnet start --node --archiver --sequencer'
    ports:
      - 40400:40400/tcp
      - 40400:40400/udp
      - 8080:8080

  volumes:
    - /home/my-node/node:/data # Local directory

Troubleshooting

L1 Access

If you're hosting your own Ethereum execution or consensus client locally (rather than using an external RPC like Alchemy), you need to ensure that the prover node inside Docker can reach it.

By default, Docker runs containers on a bridge network that isolates them from the host machine’s network interfaces. This means localhost inside the container won’t point to the host’s localhost.

To fix this:

Option 1: Use the special hostname host.docker.internal This tells Docker to route traffic from the container to the host machine. For example:

--l1-rpc-urls http://host.docker.internal:8545

Option 2: Add a host network entry to your Docker Compose file (advanced users) This gives your container direct access to the host’s network stack, but removes Docker’s network isolation. Add to your docker-compose.yml

network_mode: "host"

⚠️ Note: network_mode: "host" only works on Linux. On macOS and Windows, use host.docker.internal.

info

You can run your own Sepolia ETH Node. However, at the moment only geth and reth nodes are confirmed to work reliably with the Aztec client.

Happy sequencing!