Starknet Sepolia Node and Attestor Installation Guide

About Starknet on Sepolia

Starknet Sepolia is the public testnet. It is the right place to rehearse the validator flow, because on Sepolia the minimum validator stake is 1 STRK against 20,000 STRK on mainnet — the whole staking and attestation lifecycle can be exercised for a nominal amount.

A Starknet validator is two processes:

• a full node (Pathfinder) that follows Starknet and answers RPC;
• an attestor that watches for the blocks your validator is assigned and submits attestation transactions. Rewards depend on attestations landing, not on the node merely being up.

The dependency people miss

Pathfinder does not stand alone. It follows Starknet by reading Ethereum, so it needs an Ethereum Sepolia WebSocket endpoint for the whole time it runs — not just during sync. Choose this endpoint deliberately:

• it must be a WebSocket URL (wss://), not plain HTTPS;
• free public Sepolia endpoints will emit repeated PubSub backend errors while block import quietly continues. If catch-up stalls rather than merely logging, the endpoint is the first thing to replace, not Pathfinder;
• some providers refuse archive log requests without an account. Confirm your endpoint answers historical log queries before committing to it.

Requirements

Component	Minimum	Recommended
CPU	4 cores	8 cores
RAM	8 GB	16 GB
Disk	250 GB SSD	500 GB NVMe
Network	100 Mbps	1 Gbps
OS	Ubuntu 22.04	Ubuntu 24.04

Prepare the host

sudo apt -y update && sudo apt -y upgrade
sudo apt -y install docker.io docker-compose-v2 jq curl
sudo systemctl enable --now docker
sudo usermod -aG docker "$USER"

Run Pathfinder

Create ~/starknet-sepolia/docker-compose.yml:

services:
  pathfinder:
    image: eqlabs/pathfinder:v0.22.7
    container_name: pathfinder-testnet
    restart: unless-stopped
    ports:
      - "127.0.0.1:9545:9545"
      - "127.0.0.1:9000:9000"
    volumes:
      - ./data:/usr/share/pathfinder/data
    command:
      - --network=sepolia-testnet
      - --ethereum.url=wss://<your-ethereum-sepolia-ws-endpoint>
      - --http-rpc=0.0.0.0:9545
      - --monitor-address=0.0.0.0:9000

mkdir -p ~/starknet-sepolia/data && cd ~/starknet-sepolia
docker compose up -d
docker compose logs -f pathfinder

Pin the image to an explicit tag as shown. Bind the RPC and metrics ports to 127.0.0.1 unless you intend to publish them, and put a reverse proxy in front if you do.

Use the official snapshot

Syncing Sepolia from genesis takes days. Restore the official Pathfinder testnet-sepolia snapshot instead, then let the node catch up the remainder. Before replacing anything, move the existing database aside rather than deleting it:

docker compose down
mv ~/starknet-sepolia/data ~/starknet-sepolia/data.pre-snapshot-$(date -u +%Y%m%dT%H%M%SZ)
mkdir -p ~/starknet-sepolia/data
# download and extract the official snapshot into ./data, then:
docker compose up -d

Keeping the previous directory is what makes a bad snapshot a five-minute rollback instead of a fresh multi-day sync.

Verify

curl -s -X POST http://127.0.0.1:9545/rpc/v0_7 \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"starknet_blockNumber","params":[]}' | jq

curl -s -X POST http://127.0.0.1:9545/rpc/v0_7 \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"starknet_chainId","params":[]}' | jq

Compare your block number with a public Sepolia explorer. A node that is importing but far behind is normal during catch-up; a node whose height stops advancing is almost always the Ethereum endpoint, not Pathfinder.

Prepare the validator account

1. Create and fund a Starknet Sepolia account (a public faucet provides test STRK/ETH). Keep the keystore at mode 0600 and never print or copy the private key.
2. Deploy the account with Starkli once it holds funds — an undeployed account cannot send transactions.
3. Register as a validator with the minimum Sepolia stake (1 STRK) and set your commission.
4. Run the attestor against your own Pathfinder RPC and confirm attestations are landing on-chain. Attestation transactions cost fees, so the attestor account needs a working balance and monitoring on that balance.

Monitoring

Watch: container state and restart count, block height advancing versus a public explorer, the Ethereum Sepolia endpoint's health, attestations actually landing in each assigned window, attestor account balance, and disk free.

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Created by POSTHUMAN validators

Website: https://posthuman.digital