Geth Ethereum Node for CAS

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This guide was written using Geth version 1.13.14-stable.

• For newer versions, please consult: https://geth.ethereum.org/docs/getting-started/installing-geth

Geth is an Ethereum node execution client. Historically, an execution client alone was enough to run a full Ethereum node. However, since Ethereum swapped from proof-of-work (PoW) to proof-of-stake (PoS) based consensus in2022, Geth now needs to be coupled to another piece of software called a "consensus client". Both pieces of software must be installed to operate an Ethereum node.

Installation of the Geth Ethereum client and Prysm client on Ubuntu 22.04 LTS is described herein.

1. Install Geth as the “Execution Client”

Open

Update your server:

Add the Geth PPA repository:

Install Geth:

Verify that the installation was successful:

That command should generate a confirmation like so:

2. Startup Geth.

a) Create a new account/wallet using Geth.

Create the account:

• Use a memorable password, like “GeneralBytesIsGreat”.

Verify the account:

You may see a few errors (it’s ok), but “Account #0” should be listed at the end.

b) Start the Geth node:

SCREEN is described above: https://generalbytes.atlassian.net/wiki/spaces/ESD/pages/3156279297/Geth+Ethereum+Node+for+CAS#SCREEN

Geth will now start inside the new SCREEN window, and automatically begin searching for other nodes. It won’t begin downloading the blockchain until the next step (installing a consensus client) has completed.

• Exit SCREEN using Ctrl+A, then “d” (for detach).

  • To later return (reattach) to this window, use screen -r geth.

3. Install Prysm as the “Consensus Client”.

You may choose any Consensus Client that suits you. You have a half-dozen choices, and the community encourages diversity.

Other consensus clients: https://geth.ethereum.org/docs/getting-started/consensus-clients

For this example I chose “Prysm” because it is also based on the Go software. It was mostly an arbitrary decision. The guidance I provide below differs from the one at their website, as certain assumptions (Ubuntu + Geth + IPC + Mainnet) have already been calculated in.

Full Prysm installation instructions here: https://docs.prylabs.network/docs/install/install-with-script

a) Install Prysm:

b) Start Prysm:

Create a new SCREEN window, and start Prysm:

• The IPC endpoint specified is the Linux Geth default.

• Exit SCREEN using Ctrl+A, then “d” (for detach).

  • To later return (attach) to this window, use screen -r prysm.

4. Sync.

Now that an account has been created and a consensus client is operating, Geth & Prysm will begin to automatically synchronize it with the rest of the Ethereum network. This will take quite some time, and is unavoidable. You must be prepared to wait days before the process is complete. Once finished with the initial sync, your Node will keep itself synchronized - but the first time is lengthy.

To view the sync process, reattach to the Geth screen:

You’ll see Geth fetching blocks from other nodes, confirming the blocks, and adding them to your locally stored blockchain. This is called a “full node implementation”, and they are important to the network. Full nodes are the backbone of Ethereum (and all other blockchain-based networks).

This is an example of the node output:

• Notice the “age” and ETA reported in this log.

The synchronization may take a few days. The reported ETA is unreliable and virtually worthless. The actual ETA heavily depends upon several factors, including your CPU, GPU, RAM, storage technology, and Internet bandwidth. Once the entire blockchain has been downloaded and confirmed by your node, you’ll be ready to proceed with the next step of enabling remote access.

Once you are satisfied that the synchronization is underway, exit the SCREEN using Ctrl+A, then “d”.

Watch and wait.

The node will attempt to use all available resources to finish as quickly as possible, but your server’s host may classify it as abuse. They’ll respond by automatically “killing” your node. Here’s how to tell in the Geth Server:

If you see that, then your node was probably shut down for abusing your host’s “Terms of Service”. Yes, I was guilty of that once. Sorry Google. Explore the use of “cpulimit” to prevent that abuse, or increase the server resources to comply with your hosts demands.

The point is: check in on the process from time-to-time, and restart it (if needed). You lose nothing but time, as the download will be recovered from the moment it was killed.

Control.

To monitor the sync progress, you may use the built-in Geth JavaScript client to check up on it. Once you’ve SSH’d in to your server, start the Geth JavaScript console using:

You should see something similar to:

• The SCREEN containing the Geth Server should still be running merrily in the background.

• The Javascript console enables you to monitor & control your node; this is the front door.

• More information here: https://geth.ethereum.org/docs/interface/javascript-console

Type the following in the Javascript console to identify the synchronization progress of your node:

If your node is still synchronizing, then you’ll see something like this in the Geth Console:

• In this report, “highestBlock” is the number of blocks (total) to confirm.

• “currentBlock” is the block that your node is currently confirming.

• In the example above, block downloading is about 2857543/10633048 (26.9%) completed.

• After that completes, it will update “trie nodes” (States). This number cannot be predicted, and will be very large, each update reporting: “Imported new state entries”. This may take days itself, and your sync may seem “stuck”. It isn’t. Be patient.

Many people falsely assume that because they have the blocks, they are in sync. Unfortunately this is not the case, since no transaction was executed, so we do not have any account state available (ie. balances, nonces, smart contract code and data). These need to be downloaded separately and cross checked with the latest blocks. This phase is called the state trie download and it actually runs concurrently with the block downloads; alas it take a lot longer nowadays than downloading the blocks. - from: https://geth.ethereum.org/docs/faq

Eventually, the Geth Console query will result in a “false”, as illustrated here:

This means that your node has stopped synchronizing. This is likely because it has finished successfully, or possibly because your node has been shut down.

Ensure that the Geth Server isn’t shutdown (i.e. for abuse, see above) and that it continues to process the network. If “eth.syncing” generates a “false” reply in the Geth Console, then your blockchain is now fully synchronized and your node ready for the next step.

Backup the account.

• You will need both the backup and the password to access your wallet in case of a disaster.

• See official documentation for details.

Setup an SSH tunnel to secure inter-server RPC communication.

We discourage running any software on your CAS server (except for CAS itself). This warning includes the Geth Node Server. The simple solution is to use port forwarding to enable CAS access to your separate Geth Node Server. Two options are explained:

Option 1: (recommended) use the GB Wallet Tunnel:

General Bytes includes an integrated open-source SSH client in CAS. The client is designed to work in tandem with the GB Wallet Tunnel Server.

Click here for instructions to install the GB Wallet Tunnel Server.

Option 2: (alternative) create an SSH tunnel:

You may elect to use the native SSH tunnel for secure RPC communication with this Node:

The general usage would be:

In the above example (run from your CAS server CLI), the options explained:

• "ssh -f -N" is the "create a permanent tunnel in the background" command.

• "-i /home/gb/.ssh/cas-geth-node" specifies the SSH private key file to be used.

• "-L 8545:127.0.0.1:8545" are the Geth's default RPC ports being forwarded.

• "gb@35.237.163.176" is the SSH user (and IP) of the Node.

This presumes that your private key file is stored at /home/gb/.ssh/ as: cas-geth-node

• We do absolutely encourage password-less logins (use a private key).

• If the CAS system permits multiple users, you should password-protect the private key.

Recruit an IT professional if you are uncomfortable with any of this! Protect your funds!

Unlock your account

Locate your account address in the Geth Console by using:

Unlock the wallet using the account address from the previous step:

• Quotes are required with the address.

• “null” will cause the Geth Console to request your password. The password is not saved or visible anywhere using this method. You may also provide it in quotes, but that method may expose your wallet password, so use cautiously.

• The “0” means “leave it open”. Any other number sets the number of seconds before auto-lock, which is incompatible with CAS. CAS MUST HAVE AN UNLOCKED WALLET TO FUNCTION.

• Returns “true” if the wallet is unlocked & opened.

After the Geth Node Server is shutdown, the wallet will automatically close, but if you prefer to do it manually, the following command will accomplish that:

Once the wallet is unlocked, you may exit from the Geth Console at your leisure:

Next: Configure CAS to use this node.