Connecting to the eth2 chain

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Depending on your objective, there are various ways to run Nimbus in Ethereum 2.0 mode.

Become an eth2 validator

We’re writing a book that explains all the ways in which you can use Nimbus to either monitor the eth2 chain or become a fully-fledged validator.

It’s hosted here:

Build and run the Ethereum 2.0 local beacon chain simulation

The beacon chain simulation runs several beacon nodes on the local machine, attaches several local validators to each, and builds a beacon chain between them.

Prerequisites: At the moment, Nimbus has to be built from source, and has the following external dependencies – developer tools (C compiler, Make, Bash, Git), PCRE; follow the instructions outlined here to install them.

Once you’ve installed the prerequisites, you’re ready to enter the Ethereum 2.0 realm of Nimbus:

git clone
cd nim-beacon-chain

make test

To run the simulation:

make eth2_network_simulation

If you’d like to clean the previous run’s data:

make clean_eth2_network_simulation_all

To change the number of validators and nodes:

# Clear data files from your last run and start the simulation with a new genesis block:
make VALIDATORS=192 NODES=6 USER_NODES=1 eth2_network_simulation

If you’d like to see the nodes running on separated sub-terminals inside one big window, install Multitail (if you’re on a Mac, follow the instructions here), then:

USE_MULTITAIL="yes" make eth2_network_simulation

You’ll get something like this (click for full size):

You can find out more about the beacon node simulation here.

Build and run the Ethereum 2.0 local state transition simulation

This simulation is primarily designed for researchers, but we’ll cover it briefly here in case you’re curious :)

The state transition simulation quickly runs the beacon chain state transition function in isolation and outputs JSON snapshots of the state (directly to the nim-beacon-chain directory). It runs without networking and blocks are processed without slot time delays.

# build the state simulator, then display its help ("-d:release" speeds it
# up substantially, allowing the simulation of longer runs in reasonable time)
make NIMFLAGS="-d:release" state_sim
build/state_sim --help

Use the output of the help command to pass desired values to the simulator - experiment with changing the number of slots, validators, , etc. to get different results.

The most important options are:

  • slots : the number of slots to run the simulation for (default 192)
  • validators: the number of validators (default 6400)
  • attesterRatio: the expected fraction of attesters that actually do their work for every slot (default 0.73)
  • json_interval: how often JSON snapshots of the state are outputted (default every 32 slots – or once per epoch)

For example, to run the state simulator for 384 slots, with 20,000 validators, and an average of 66% of attesters doing their work every slot, while outputting snapshots of the state twice per epoch, run:

build/state_sim --slots=384 --validators=20000 --attesterRatio=0.66 --json_interval=16

Medalla Ethereum 2.0 Testnet

There is a publicly available Ethereum 2.0 multi-client testnet currently running. Read all about it here, and learn how you can join it in the Nimbus beacon chain book 💛