SimApp

SimApp is a CLI application built using the Cosmos SDK for testing and educational purposes.

Running Testnets with simd

Want to spin up a quick testnet with your friends? Follow these steps. Unless stated otherwise, all participants in the testnet must follow through with each step.

1. Download and Setup

Download IBC-go and unzip it. You can do this manually (via the GitHub UI) or with the git clone command:

git clone github.com/cosmos/ibc-go.git

Next, run this command to build the simd binary in the build directory:

make build

Use the following command and skip all the next steps to configure your SimApp node:

make init-simapp

If you've run simd in the past, you may need to reset your database before starting up a new testnet. You can do that with this command:

# you need to provide the moniker and chain ID
$ ./simd init [moniker] --chain-id [chain-id]

The command should initialize a new working directory at the ~simapp location. The moniker and chain-id can be anything, but you must use the same chain-id subsequently.

2. Create a New Key

Execute this command to create a new key:

 ./simd keys add [key_name]

⚠️ The command will create a new key with your chosen name. Save the output somewhere safe; you'll need the address later.

3. Add Genesis Account

Add a genesis account to your testnet blockchain:

./simd genesis add-genesis-account [key_name] [amount]

Where key_name is the same key name as before, and the amount is something like 10000000000000000000000000stake.

4. Add the Genesis Transaction

This creates the genesis transaction for your testnet chain:

./simd genesis gentx [key_name] [amount] --chain-id [chain-id]

The amount should be at least 1000000000stake. Providing too much or too little may result in errors when you start your node.

5. Create the Genesis File

A participant must create the genesis file genesis.json with every participant's transaction. You can do this by gathering all the Genesis transactions under config/gentx and then executing this command:

./simd genesis collect-gentxs

The command will create a new genesis.json file that includes data from all the validators. We sometimes call this the "super genesis file" to distinguish it from single-validator genesis files.

Once you've received the super genesis file, overwrite your original genesis.json file with the new super genesis.json.

Modify your config/config.toml (in the simapp working directory) to include the other participants as persistent peers:

# Comma-separated list of nodes to keep persistent connections to
persistent_peers = "[validator_address]@[ip_address]:[port],[validator_address]@[ip_address]:[port]"

You can find validator_address by executing:

./simd comet show-node-id

The output will be the hex-encoded validator_address. The default port is 26656.

6. Start the Nodes

Finally, execute this command to start your nodes:

./simd start

Now you have a small testnet that you can use to try out changes to the Cosmos SDK or CometBFT!

⚠️ NOTE: Sometimes, creating the network through the collect-gentxs will fail, and validators will start in a funny state (and then panic).

If this happens, you can try to create and start the network first with a single validator and then add additional validators using a create-validator transaction.