Sepolia Testnet

This guide is a recommended way of running your node, specifically as a systemd service on a Linux-based machine (be it virtual, or bare metal) and is complementary to the official documentation available here. You could also start your node as a Docker container, but we would recommend using this option only if you are familiar with container technologies and we strongly encourage leveraging the power of containers with an orchestration software such as Kubernetes.

• Official Docs
• Github Repository

Recommended Hardware Specifications

AWS:

• m5.xlarge or any equivalent instance type

Bare Metal:

• 16GB RAM
• 4 vCPUs
• At least 1.2TB SSD of storage - make sure it's extendable (~3GB daily storage growth)

Assumptions

We're going to assume you are already logged into your Virtual Machine as a privileged user or as the root user.

Setup

After making sure your operating system is up to date we will need to install a couple of packages before actually getting the node started.

sudo apt-get update && sudo apt-get upgrade -y
sudo apt-get install git curl wget cmake build-essential clang ufw jq net-tools lz4 -y

The easiest way to get the nitro binary is to copy it directly from the latest official Docker image.

# install Docker
sudo apt-get remove docker docker-engine docker.io containerd runc -y
sudo apt-get install ca-certificates curl gnupg lsb-release -y
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
echo   "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
    $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io -y

# pull latest Nitro image
LATEST_RELEASE="v2.0.14-2baa834"
docker pull offchainlabs/nitro-node:${LATEST_RELEASE}

# copy binary from image
docker cp $(docker run -it -d offchainlabs/nitro-node:${LATEST_RELEASE}):/usr/local/bin/nitro /usr/local/bin/nitro

Since Arbitrum is an L2 blockchain, you will also need access to an L1 RPC, in this case Ethereum Sepolia. You can run your own node as instructed here or you can get an Ethereum Sepolia endpoint from Blast.

The next step is to create the systemd configuration file:

sudo touch /etc/systemd/system/arbitrum.service # create the file
sudo vi /etc/systemd/system/arbitrum.service # open the file for writing - we prefer vi as our text editor, but feel free to use what suits you best

The contents of the systemd configuration file should be:

[Unit]
Description=Arbitrum Node Service
[Service]
Type=simple
User=<USER> # replace <USER> with your user
ExecStart=/usr/local/bin/nitro \
          --l1.url <YOUR_ETHEREUM_ENDPOINT_URL> # e.g. https://eth-sepolia.blastapi.io/<UUID>
          --l2.chain-id 421614 # Arbitrum Nova chain ID
          --node.rpc.evm-timeout=10s
          --http.api=net,web3,eth
          --http.corsdomain=*
          --http.addr=0.0.0.0
          --http.port=8545
          --http.vhosts=*
          --ws.addr=0.0.0.0
          --ws.api=net,web3,eth
          --ws.port=8546
          --ws.origins=*
          --metrics
          --metrics-server.addr 0.0.0.0
          --metrics-server.port 6070
LimitNOFILE=65536
Restart=on-failure
RestartSec=30
TimeoutStopSec=45
[Install]
WantedBy=multi-user.target

Please make sure that the RPC and WS ports are accessible (in this case - 8545 for RPC & 8546 for WS).

That's pretty much it. We can now start the service, and implicitly the node.

sudo systemctl daemon-reload
sudo systemctl enable arbitrum.service
sudo systemctl start arbitrum.service

You can check if the service is running properly as follows:

sudo systemctl status arbitrum.service # check if the service is active and running
sudo journalctl -f -u arbitrum.service # check the logs of the node

The node should now be syncing with the network. If you do not wish to sync from scratch (which should take a few days), you can use the Arbitrum Snapshots provided by the Arbitrum Foundation, which we've successfully used in the past for various use cases. It is important to know that your node should be stopped while downloading the snapshots and it is important that the database files are cleaned up before downloading to ensure data integrity. You should also check the official docs for more details regarding the database snapshots here.

You can check if the node is synced by running the RPC call listed below from inside your environment. You are going to need to have the curl package installed for this, so make sure to install it beforehand.

curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}' localhost:8545

The result should be a hex number (i.e 0x10c5815). If you convert it to a decimal number, you can compare it to the latest block listed on the explorer.

In order to test the WS endpoint, we will need to install a package called node-ws.

An example WS call would look like this:

wscat --connect ws://localhost:8546
> {"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}

Monitoring Guidelines

In order to maintain a healthy node that passes the Integrity Protocol's checks, you should have a monitoring system in place. Blockchain nodes usually offer metrics regarding the node's behaviour and health - a popular way to offer these metrics is Prometheus-like metrics. The most popular monitoring stack, which is also open source, consists of:

• Prometheus - scrapes and stores metrics as time series data (blockchain nodes cand send the metrics to it);
• Grafana - allows querying, visualization and alerting based on metrics (can use Prometheus as a data source);
• Alertmanager - handles alerting (can use Prometheus metrics as data for creating alerts);
• Node Exporter - exposes hardware and kernel-related metrics (can send the metrics to Prometheus).

We will assume that Prometheus/Grafana/Alertmanager are already installed (we will provide a detailed guide of how to set up monitoring and alerting with the Prometheus + Grafana stack at a later time; for now, if you do not have the stack already installed, please follow this official basic guide here).

We recommend installing the Node Exporter utilitary since it offers valuable information regarding CPU, RAM & storage. This way, you will be able to monitor possible hardware bottlenecks, or to check if your node is underutilized - you could use these valuable insights to take decisions regarding scaling up/down the allocated hardware resources.

Below, you can find a script that installs Node Exporter as a systemd service.

#!/bin/bash

# set the latest version
VERSION=1.6.1

# download and untar the binary
wget https://github.com/prometheus/node_exporter/releases/download/v${VERSION}/node_exporter-${VERSION}.linux-amd64.tar.gz
tar xvf node_exporter-*.tar.gz
sudo cp ./node_exporter-${VERSION}.linux-amd64/node_exporter /usr/local/bin/

# create system user
sudo useradd --no-create-home --shell /usr/sbin/nologin node_exporter

# change ownership of node exporter binary
sudo chown node_exporter:node_exporter /usr/local/bin/node_exporter

# remove temporary files
rm -rf ./node_exporter*

# create systemd service file
cat > /etc/systemd/system/node_exporter.service <<EOF
[Unit]
Description=Node Exporter
Wants=network-online.target
After=network-online.target
[Service]
User=node_exporter
Group=node_exporter
Type=simple
ExecStart=/usr/local/bin/node_exporter
[Install]
WantedBy=multi-user.target
EOF

# enable the node exporter service and start it
sudo systemctl daemon-reload
sudo systemctl enable node_exporter.service
sudo systemctl start node_exporter.service

As a reminder, Node Exporter uses port 9100 by default, so be sure to expose this port to the machine which holds the Prometheus server. The same should be done for the metrics port(s) of the blockchain node (in this case, we should expose ports 9101 - for monitoring the parachain).

Having installed Node Exporter and having already exposed the node's metrics, these should be added as targets under the scrape_configs section in your Prometheus configuration file (i.e. /etc/prometheus/prometheus.yml), before reloading the new config (either by restarting or reloading the config - please check the official documentation). This should look similar to this:

scrape_configs:
  - job_name: 'arbitrum-sepolia-node'
    scrape_interval: 10s
    metrics_path: /metrics
    static_configs:
      - targets:
        - '<NODE0_IP>:6070'
        - '<NODE1_IP>:6070' # you can add any number of nodes as targets
  - job_name: 'arbitrum-sepolia-node-exporter'
    scrape_interval: 10s
    metrics_path: /metrics
    static_configs:
      - targets:
        - '<NODE0_IP>:9100'
        - '<NODE1_IP>:9100' # you can add any number of nodes as targets

In the configuration file above, please replace:

• <NODE0_IP> - node 0's IP
• <NODE1_IP> - node 1's IP (you can add any number of nodes as targets)
• ...
• <NODEN_IP> - node N's IP (you can add any number of nodes as targets)

That being said, the most important metrics that should be checked are:

• node_cpu_seconds_total - CPU metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:
  • 100 - (avg by (instance) (rate(node_cpu_seconds_total{job="arbitrum-sepolia-node-exporter",mode="idle"}[5m])) * 100), which means the average percentage of CPU usage over the last 5 minutes;
• node_memory_MemTotal_bytes/node_memory_MemAvailable_bytes - RAM metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:
  • (node_memory_MemTotal_bytes{job="arbitrum-sepolia-node-exporter"} - node_memory_MemAvailable_bytes{job="arbitrum-sepolia-node-exporter"}) / 1073741824, which means the amount of RAM (in GB) used, excluding cache/buffers;
• node_network_receive_bytes_total - network traffic metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:
  • rate(node_network_receive_bytes_total{job="arbitrum-sepolia-node-exporter"}[1m]), which means the average network traffic received, per second, over the last minute (in bytes);
• node_filesystem_avail_bytes - FS metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:
  • node_filesystem_avail_bytes{job="arbitrum-sepolia-node-exporter",device="<DEVICE>"} / 1073741824, which means the filesystem space available to non-root users (in GB) for a certain device <DEVICE> (i.e. /dev/sda or wherever the blockchain data is stored) - this can be used to get an alert whenever the available space left is below a certain threshold (please be careful how you choose this threshold: if you have storage that can easily be increased - for example, EBS storage from AWS, you can set a lower threshold, but if you run your node on a bare metal machine which is not easily upgradable, you should set a higher treshold just to be sure you are able to find a solution before it fills up);
• up - Prometheus automatically generated metrics - for monitoring purposes, you could use the following expressions:
  • up{job="arbitrum-sepolia-node"}, which has 2 possible values: 1, if the node is up, or 0, if the node is down - this can be used to get an alert whenever the node goes down (i.e. it can be triggered at each restart of the node);
• chain_head_block - metrics exposed by the node - for monitoring purposes, you could use the following expressions:
  • increase(chain_head_block{job="arbitrum-sepolia-node"}[1m]), which means the amount of blocked produced in the last minute - this can be used to get an alert whenever the node is stuck (not syncing anymore) or the blockchain has issues (e.g. is halted) (you should expect hundreds of new blocks per minute, so this could be the threshold for the alert to be triggered).

info

Please make sure to also check the Official Documentation and the Github Repository posted above in order to make sure you are keeping your node up to date.