Become a Validator: Using Docker

Sigma Prime maintains the sigp/lighthouse-docker repository which provides an easy way to run Lighthouse without building the Lighthouse binary yourself.

Note: when you're running the Docker Hub image you're relying upon a pre-built binary instead of building from source. If you want the highest assurance you're running the real Lighthouse, build the docker image yourself instead. You'll need some experience with docker-compose to integrate your locally built docker image with the docker-compose environment.

0. Install Docker Compose

Docker Compose relies on Docker Engine for any meaningful work, so make sure you have Docker Engine installed either locally or remote, depending on your setup.

For more on installing Compose, see here.

1. Clone the repository

Once you have Docker Compose installed, clone the sigp/lighthouse-docker repository:

 git clone https://github.com/sigp/lighthouse-docker
 cd lighthouse-docker

2. Configure the Docker environment

Then, create a file named .env with the following contents (these values are documented here):

DEBUG_LEVEL=info
START_GETH=true
START_VALIDATOR=true
VALIDATOR_COUNT=1
VOTING_ETH1_NODE=http://geth:8545

To specify a non-default testnet add TESTNET=<testnet> to the above file. can be altona or medalla.

This .env file should live in the lighthouse-docker directory alongside the docker-compose.yml file.

3. Start Lighthouse

Start the docker-compose environment (you may need to prefix the below command with sudo):

 docker-compose up

Watch the output of this command for the Decrypted validator keystore pubkey log, as it contains your voting_pubkey -- the primary identifier for your new validator. This key is useful for finding your validator in block explorers. Here's an example of the log:

validator_client_1  | Jun 01 00:29:24.418 INFO Decrypted validator keystore      voting_pubkey: 0x9986ade7a974d2fe2d0fc84a8c04153873337d533d43a83439cab8ec276410686dd69aa808605a7324f34e52497a3f41

This is one of the earlier logs outputted, so you may have to scroll up or perform a search in your terminal to find it.

Note: docker-compose up generates a new sub-directory -- to store your validator's deposit data, along with its voting and withdrawal keys -- in the lighthouse-data/validators directory. This sub-directory is identified by your validator's voting_pubkey (the same voting_pubkey you see in the logs). So this is another way you can find it.

Note: the docker-compose setup includes a fast-synced geth node. So you can expect the beacon_node to log some eth1-related errors whilst the geth node boots and becomes synced. This will only happen on the first start of the compose environment or if geth loses sync.

Note: If you are participating in the genesis of a network (the network has not launched yet) you will notice errors in the validator client. This is because the beacon node not expose its HTTP API until the genesis of the network is known (approx 2 days before the network launches).

To find an estimate for how long your beacon node will take to finish syncing, look for logs that look like this:

beacon_node_1       | Mar 16 11:33:53.979 INFO Syncing
est_time: 47 mins, speed: 16.67 slots/sec, distance: 47296 slots (7 days 14 hrs), peers: 3, service: slot_notifier

You'll find the estimated time under est_time. In the example above, that's 47 mins.

If your beacon node hasn't finished syncing yet, you'll see some ERRO messages indicating that your node hasn't synced yet:

validator_client_1  | Mar 16 11:34:36.086 ERRO Beacon node is not synced               current_epoch: 6999, node_head_epoch: 5531, service: duties

It's safest to wait for your node to sync before moving on to the next step, otherwise your validator may activate before you're able to produce blocks and attestations (and you may be penalized as a result).

However, since it generally takes somewhere between 4 and 8 hours after depositing for a validator to become active, if your est_time is less than 4 hours, you should be fine to just move on to the next step. After all, this is a testnet and you're only risking Goerli ETH!

Installation complete!

In the next step you'll need to upload your validator's deposit data. This data is stored in a file called eth1_deposit_data.rlp.

You'll find it in lighthouse-docker/.lighthouse/validators/ -- in the sub-directory that corresponds to your validator's public key (voting_pubkey).

For example, if you ran step 1 in /home/karlm/, and your validator's voting_pubkey is 0x8592c7.., then you'll find your eth1_deposit_data.rlp file in the following directory:

/home/karlm/lighthouse-docker/.lighthouse/validators/0x8592c7../

Once you've located eth1_deposit_data.rlp, you're ready to move on to Become a Validator: Step 2.