RSK Workshop: Pre-requisites

Several RSK workshops have common pre-requisites that you will need to have set up or configured on your system before proceeding. Here are some detailed instructions on how to prepare ahead of your next workshop.

Some workshops will require all of the following items, and some may only require a subset of the following items. Each workshop should have a “pre-requisites” section and specify which ones are which.

POSIX compliant shell

  • Mac OSX and Linux distributions: Use the standard terminal
  • Windows: If you use the standard cmd terminal, or PowerShell, the commands here may not work. Consider installing Git for Windows, which comes with Git Bash bundled. Here’s a great tutorial on installing and using Git Bash.


  • The most fuss-free way to install and manage multiple versions of node on your computer is nvm.
  • This tutorial assumes that you have version 12 or later
nvm install 12
nvm use 12


  • Install truffle
  • Install mnemonics, which is a simple utility that can be used to generate BIP39 mnemonics

Use the following command.

npm i -g truffle@5.1.22 mnemonics@1.1.3

Note that mnemonics is not part of the Truffle suite, however several workshops use this in conjunction with Truffle.


  • You will need Java 8 in order to run RSKj
  • If java -version displays an error, or displays a version other than 1.8, you will need to install it.

There are a variety of ways to do this, and SDKman is one which allows you to install and switch between multiple versions as needed:

curl -s "" | bash
source "$HOME/.sdkman/bin/"
# to get a filtered list of available java versions
sdk list java  | grep "8\."
# copy one of the options listed for use below, e.g. 8.0.242.j9-adpt

# install the version of java copied above
# (replace accordingly)
sdk install java 8.0.242.j9-adpt

# show installed versions, and switch to the selected one
# (replace accordingly)
sdk list java | grep installed
sdk use java 8.0.242.j9-adpt
java -version


  • This is a system command that is likely already installed on your system
  • If curl --version displays an error, download curl.

Code editor

  • Software that is able to edit text files
  • Preferably one that has support for syntax highlighting for both Solidity and Javascript
  • VS Code is a good choice if you don’t already have one


Get RSKj running locally.

This will provide you with a localhost-only network, for fast testing, called Regtest. The same node also can connect to permissionless decentralised networks of peer nodes also running RSKj - Testnet and Mainnet.

For this part, open up a new shell, as you will need to leave the RSKj process running in the background while you continue with other tasks in the foreground.

mkdir -p ~/code/rsk/rskj-node
cd ~/code/rsk/rskj-node
curl \
  -L \ \
  > ./rskj-core-2.0.1-PAPYRUS-all.jar
sha256sum rskj-core-2.0.1-PAPYRUS-all.jar
# 43149abce0a737341a0b063f2016a1e73dae19b8af8f2e54657326ac8eedc8a0 rskj-core-2.0.1-PAPYRUS-all.jar

Note: When installing and running the RSKj node, it is always a good idea to verify that your copy is legitimate. Full instructions on how to do this.

For the purposes of this workshop, we will run RSKj on Regtest.

java -cp rskj-core-2.0.1-PAPYRUS-all.jar -Drpc.providers.web.cors=* co.rsk.Start --regtest

If you see no output - that is a good thing: Its output is directed to a log file.

Note the flag provided above: -Drpc.providers.web.cors=* This disables cross origin resource sharing protection, effectively allowing any web page to access it. As we want to make JSON-RPC requests from a browser, such as a DApp, we need this flag.

Note that if you see an error similar to the following, you will need to clear your Regtest data directory from an older version of RSKj.

A block header must have 16/17 elements or 19/20 including merged-mining fields but it had 19

To do so, simply delete the .rsk/regtest directory within your home directory, using the following command.

rm -rf ~/.rsk/regtest/

Leave this running in an open shell, and switch back to your original shell for the rest of this workshop.

Back in your original shell, it is a good idea to verify that you are able to successfully make JSON-RPC requests before proceeding.

curl \
  http://localhost:4444/ \
  -s -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

If this command fails, it is likely that the Regtest node running locally (running on your own computer) is not working properly. You should see a response similar to the following:


Now let’s do the same thing, but this time, instead of connecting to something running locally, we connect to the RSK Testnet. You can run your own RSK Testnet node using the same RSKj used earlier, or you can simply connect to public node. THe latter option requires no setup, and that is what we’ll be doing:

curl \ \
  -s -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

You should see a response similar to the following:


If this command fails, it is likely that your connection to RSK’s public node is impeded in some way, and you should identify and relax any restrictive network firewall or proxy rules.

The result property is the number of the latest block that has been synced. Note that this value (0xca035) is the block number in hexadecimal (base 16), so the output above indicates that the current block number is 827445 in decimal (base 10). This should match the “Best Block” field in the RSK Testnet Stats site.