DevNews: AWS 101 — Basic Configuration for Validator Nodes

In this new series of DevNews articles, we’re going to be covering some basic configurations for the three main Cloud platforms: AWS, Google Cloud and Microsoft Azure. We’ll spin up a full node, connect it to the network and turn the full node into a Validator node.

This first article introduces a very simple “quick start” single AWS EC2 instance, using a VPC with a single public subnet. Validator node operators are highly encouraged to explore more sophisticated architecture configurations to increase the security, reliability and availability of their Validator node — for example, multi layered network with both private/public subnets, one or more “sentry” full (non-validator) nodes placed in front of your main (hidden in a private subnet) Validator node to handle and relay communication from the outside world, and reverse proxy for any RPC access via the sentries etc. in addition to investigating implementing hardware KMS solutions to protect validator private keys.

This guide should not be considered the default, full, out of the box solution for a Validator node, but more an “AWS 101” guide to familiarise the reader with the core concepts involved in setting up the minimum AWS EC2 instance and associated service requirements in order to operate a UND Validator node. It should be considered a starting point giving you the initial building blocks from which to build a more sophisticated network/node architecture to support and protect your Validator node.

Please note: any public IPs generated by AWS during this guide are not static — they will change if the EC2 instance is restarted. It is recommended that the reader also investigates AWS’s “elastic IPs” (static IPs) for their public-facing node(s).

Where the guide prompts users to open a terminal, Windows 10 users should use PowerShell.

This guide assume the reader already has an AWS account.

Part 1: Create an SSH key pair

In order to configure your node(s) and install the necessary software, you will be connecting to the instance via SSH. SSH connections to an EC2 instance must be authenticated using an SSH Key Pair — password authentication is (and should be) disabled for security.

1. In the AWS Console, go to the EC2 dashboard and in the left menu, under “Network & Security”, click “Key Pairs” followed by the “Create Key Pair” button.
2. Enter a suitable name, for example aws-ec2-und-validator-node. Leave the file format as “pem”, and click the “Crete key pair” button.

This will download a private key called aws-ec2-und-validator-node.pem (or whatever you called it) which will be used to log into your EC2 instance via SSH.

IMPORTANT: Do not lose this key — it is used to access your node’s EC2 instance via SSH, and there is no way to recover it from the AWS console if it’s lost. Keep is safe, keep is secure, keep it secret!

Open a terminal on your local PC, and check if you have a $HOME/.ssh directory:

$ ls -la $HOME/.ssh

If you do not have a $HOME/.ssh directory, create it:

$ mkdir $HOME/.ssh
$ chmod 700 $HOME/.ssh

Next, move the downloaded private key into the $HOME/.ssh directory, and tighten the file’s permissions, replacing any bold text appropriately:

$ mv /path/to/aws-ec2-und-validator-node.pem $HOME/.ssh
$ cd $HOME/.ssh
$ chmod 400 aws-ec2-und-validator-node.pem

Part 2: Create a VPC (Network)

We need to create a network for our node. This will be a simple VPC with a single public subnet. Validator operators are encouraged to explore more sophisticated configurations for their production node.

1. From the Services menu (top-left in the header) in AWS Console, scroll down to “Networking & Content Delivery” and click “VPC”, then click the “Launch VPC Wizard” button.
2. Select the “VPC with a single public subnet” and click “Select”
3. Leave the defaults and choose a suitable name in the “VPC Name” section.
4. Choose a more descriptive name for the Subnet, then click the “Create VPC” button.

The names you choose can be anything, but should make the VPC and subnet easily identifiable to you. These names will not be public and only visible to you through the AWS console.

Next, we need to configure the VPC to automatically assign a public IP to instances in the network.

1. In the left menu of the VPC Dashboard, click “Subnets”.
2. Select your new subnet from the list, and click the “Actions” dropdown, followed by “Modify auto-assign IP settings”.
3. Tick the “Auto assign IPv4” box, and click “Save”.

Part 3: Create and launch an EC2 instance

The EC2 instance is the Virtual Machine where the node will be installed an run. We’ll create and launch a single Linux instance, and connect it to the network created in the previous part.

1. From the Services menu in AWS Console, click “EC2” under “Compute”, followed by the “Launch Instance” button.
2. On the “1. Choose AMI” tab, use the search input to find the official CentOS 7 AMI — search for “CentOS 7”. Click “AWS Marketplace” in the results, find “CentOS 7 x86_64” by centos.org (it should be the first in the results) and click the “Select” button.
3. On the “2. Choose Instance Type” tab, tick t2.micro and click “Next: Configure Instance Details”.
4. In the “Network” section, select the VPC created in the previous part. Leave the rest as the defaults, and click “4. Add Storage”, or the “Next: Add Storage” button.
5. Currently, you will need at least 30–40Gb SSD. Increase the size accordingly, or add a new volume. Click the “6. Configure Security Group” tab at the top.
6. Give the security group a meaningful name and description — for example “und-validator-node”. You will be able to find and edit this security group in the AWS EC2 console, under “Network & Security -> Security Groups” once it has been created.

Next, we need to configure some firewall rules for the instance. There is already a default rule for SSH (port 22) access, but this needs tightening to restrict SSH access. We also need to add rules for P2P so the node can communicate with other nodes, and RPC so that you can broadcast Txs to your own node.

1. In the “Source” column, for the SSH rule, click the dropdown that currently says “Custom” and select “My IP”. This will ensure only your computer’s IP can log in via SSH. Keep in mind, you will need to update this value if you do not have a static IP for your PC. This step is important, since the default value of 0.0.0.0/0 means that anyone, anywhere can attempt to access your EC2 instance via SSH. Note: if your IP changes, you will need to update this value.
2. Add a description, for example “SSH for my PC”
3. Click “Add Rule”

• Leave the “type” as “Custom TCP Rule”
• Leave the “Protocol” as “TCP
• Set the Port Range as 26656
• Click the drop-down in the Source column and select “Anywhere”
• Set the description as something like “UND Node P2P”

4. Click “Add Rule”

• Leave the “type” as “Custom TCP Rule”
• Leave the “Protocol” as “TCP
• Set the Port Range as 26657
• Click the drop-down in the Source column and select “My IP” (you want to restrict sending Txs to the node to your own IP)
• Set the description as something like “UND Node RPC”
• Note: port 26657 can be closed on your Validator node once you have registered your validator.

5. Next, if you didn’t previously, click on the ”4. Add Storage” tab.

• Change the size from 10 to 40 Gb.
• Optionally, configure disk encryption.
• Optionally, add an additional volume (around 50–100Gb) instead of increasing the size of the root volume.

6. Click “Review and Launch”

7. Review the details are correct, then click “Launch”. This will prompt you to select a key pair to use on the instance. Select the key you created in Part 1.

8. Once launched, make a note of the instance ID (top box titled “Your instances are now launching”), click your instance ID link in the same box. This will take you to the Instances console, with your new instance already highlighted. Click the pencil icon in the “Name” column, and give your instance a name.

Finally, make a note of the “IPv4 Public IP” value for your instance — you will need this to log in via SSH in the next part.

Part 4: Log in and configure instance via SSH

We now need to log in to the EC2 instance, install the prerequisites, then install and configure the UND node software. This will all be done via SSH.

Note: any bold_text in the following commands should be replaced with your own values. For example, aws-ec2-und-validator-node.pem should be replaced with the name of the file downloaded in Part 1, and vm_ip with the public IP address of your EC2 instance.

The default username for our CentOS EC2 instance is centos.

Note for Windows users: Windows 10 should have an SSH client available in the PowerShell terminal. Older Windows versions will require PuTTY.

In a terminal on your local PC, run the following:

$ ssh -i $HOME/.ssh/aws-ec2-und-validator-node.pem centos@vm_ip

This will log you in to the EC2 instance via SSH.

Part 4.1: Install the prerequisites

Once logged in to the VM via SSH, run:

$ sudo yum update -y

Install EPEL:

$ sudo yum install epel-release -y

Finally, install the following additional software:

$ sudo yum install nano jq -y

Part 4.2: Install the und binary

We have a shell script available in the mainchain GitHub repository which will automatically download and install the latest version of und. While still logged in to the instance via SSH, run the following:

$ sh -c "$(curl -sfSL https://git.io/JvHZO)"

This should install the binary into /usr/local/bin/und. Verify the installation was successful:

$ which und

should output:

/usr/local/bin/und

and:

$ und version --long

should output something similar to:

name: UndMainchain
server_name: und
client_name: undcli
version: 1.4.1
commit: 0d0538747bd2e28d363eae5bd9f95184c3be1a8e
build_tags: netgo ledger
go: go version go1.13.3 linux/amd64

Part 5: Initialising your full node

We’ll now initialise and configure the und node itself. As previously, any bold_text in the following commands should be replaced with your own values accordingly. If you are not currently logged in to the EC2 instance via SSH, do so.

Once logged in, run:

$ und init your_node_tag

your_node_tag can be any ID you like (alphanumeric characters, hyphens and underscores)

IMPORTANT: There is a known issue with the syncable pruning option in the Cosmos SDK. Since pruning = “syncable” is the default value when und init is run, it is recommended to set the value to either pruning = “everything" or pruning = “nothing" in $HOME/.und_mainchain/config/app.toml. Note that setting to pruning = “nothing”will increase storage usage considerably.

Download the latest Genesis file. The following command downloads the latest UND-Mainchain-TestNet genesis. Command is all one line:

$ curl https://raw.githubusercontent.com/unification-com/testnet/master/latest/genesis.json > $HOME/.und_mainchain/config/genesis.json

Get the current chain ID from genesis. Make a note of the output, it’ll be required in commands later in the guide. Command is all on one line:

$ jq --raw-output '.chain_id' $HOME/.und_mainchain/config/genesis.json

Next, we need the seed node info. This will allow your node to bootstrap some initial peers and connect to the network. Go to https://github.com/unification-com/testnet/blob/master/latest/seed_nodes.md and copy one or more of the seed nodes (you need the id@address:port)

Edit your node configuration file using nano:

$ nano $HOME/.und_mainchain/config/config.toml

Hit Ctrl+W, type [p2p](including the square brackets) and hit return — this will take you to the[p2p]section of the config file, which begins with:

##### peer to peer configuration options #####
[p2p]

Find the external_address = “” variable about 9 lines below, and set it to your vm_ip:26656 e.g.:

external_address = "11.22.33.44:26656"

Find the seeds = “” variable about 12 lines below, and add the seed node information between the double quotes (comma separated, no spaces if more than one). For example:

seeds = "node_id@ip:port"

Next, hit Ctrl+W, type [rpc](including the square brackets) and hit return — this will take you to the[rpc]section of the config file, which begins with:

##### rpc server configuration options #####
[rpc]

About 3 lines under this, find:

laddr = "tcp://127.0.0.1:26657"

Change the value to:

laddr = "tcp://0.0.0.0:26657"

Hit Ctrl+X followed by y and then return to save the file and exit nano.

Note: you can revert the [rpc] configuration for port 26657 to:

laddr = “tcp://127.0.0.1:26657”

once you have run the create-validator command. Broadcasting transactions can be done via a public RPC node, or, more securely, via a full node running on your local PC. See Part 8: Final cleanup for further details.

Gas Prices & Pruning

It is good practice to set the minimum-gas-prices value in $HOME/.und_mainchain/config/app.toml , in order to protect your full node from spam transactions. This should be set as a decimal value in nund, and the recommended value is currently 0.25nund. This means your node will ignore any Txs with a gas price below this value. To do so, open up $HOME/.und_mainchain/config/app.toml in a text editor, and set minimum-gas-prices

$ nano $HOME/.und_mainchain/config/app.toml

Change:

minimum-gas-prices = ""

To, for example:

minimum-gas-prices = "0.25nund"

Also, modify the pruning setting at the end of the file.

Change:

pruning = "syncable"

To:

pruning = "everything"

Hit Ctrl+X followed by y and then return to save the file and exit nano.

Finally, check that your node can connect to and sync with the network:

$ und start

The following output just means that the seed node has sent its peer address data to your node, and closed its connection:

E[2020-03-19|09:42:06.072] Stopping peer for error                      module=p2p peer="Peer{MConn{1.2.3.4:26656} dcff5de69dcc170b28b6628a1336d420f7eb60c0 out}" err=EOF

After a few seconds, you should see your node start downloading the blocks.

Hit Ctrl+C to stop the node — it will be configured as a background service next.

======================================== IMPORTANT: keep your $HOME/.und_mainchain/config/node_key.json and $HOME/.und_mainchain/config/priv_validator_key.json files safe! These are required for your node to propose and sign blocks. If you ever migrate your node to a different host/VM instance, you will need these. ========================================

Part 6: Running und as a daemon

Once you have initialised and tested the und node, it can be set up as a background daemon on the server using systemctl. This means that you can easily start/stop/restart the service, and do not need to leave the SSH session open while und is running.

If you’re not logged in to your EC2 instance via SSH, log in. If you are still logged in, and have not stopped the und node, hit Ctrl+C to stop the node.

We need to use the nano text editor to create the service configuration. Run:

$ sudo nano /etc/systemd/system/und.service

Add the following:

[Unit]
Description=Unification Mainchain Validator Node
[Service]
User=centos
Group=centos
WorkingDirectory=/home/centos
ExecStart=/usr/local/bin/und start --home=/home/centos/.und_mainchain
[Install]
WantedBy=default.target

Note: the ExecStart= is all one line.

Hit Ctrl+X followed by y and then return to save the file and exit nano.

Run:

$ sudo systemctl daemon-reload

to update systemctl

You can now start and stop the und daemon in the background using:

$ sudo systemctl start und
$ sudo systemctl stop und

Finally, you can monitor the log output for the service by running:

$ sudo journalctl -u und --follow

and use Ctrl+C to exit the journalctl command. You can now log out of your SSH session and und will continue running in the background.

Part 7: Become a Validator

Important: ensure your node has fully synced with the network before continuing.

If not already logged in, log in to your EC2 instance via SSH, and run:

$ sudo journalctl -u und --follow

Once fully synced (check the downloaded height against the current clock in the block explorer), hit Ctrl+C to quit journalctl ( und will continue to run in the background).

You will need your Validator node’s Tendermint public key in order to register it on the Mainchain network as a validator. Whilst still in the SSH session, run:

$ und tendermint show-validator

Make a note of the output, as you will need this in later commands, where it will be referred to as you_validator_public_key.

You can now exit the SSH session — the rest of the commands will be run in a terminal on your local PC.

Go to https://github.com/unification-com/mainchain/releases/latest and download the latest undcli archive for your OS — for example, undcli_v1.4.1_windows_x86_64.tar.gz. You do not need to download the und archive. Extract the archive to a suitable location.

Open a terminal/PowerShell, and cd into the directory where you extracted the undcli executable:

$ cd path/to/extracted/undcli_directory

As previously, any bold_text in the following commands should be replaced with your own values accordingly.

If you do not already have a wallet/account, you can create one (on your local PC, not in the SSH session) by running:

$ ./undcli keys add account_name

If you already have a wallet, you can import the account using:

$ ./undcli keys add account_name --recover

in which case, you will be prompted for the mnemonic and a password to secure the wallet.

From here, it is assumed the reader has an account with sufficient UND from which to self-delegate and create their Validator node. The account you use to self-delegate will become the “owner” account of the Validator node.

On your local PC, run the following command, replacing any bold_text accordingly with your own values:

./undcli tx staking create-validator \
--amount=stake_in_nund \
--pubkey=your_validator_public_key \
--moniker="your_ev_moniker" \
--website="your_website" \
--details="description" \
--security-contact="security_email" \
--chain-id=chain_id \
--commission-rate="0.10" \
--commission-max-rate="0.20" \
--commission-max-change-rate="0.01" \
--min-self-delegation="1" \
--gas="auto" \
--gas-prices="0.25nund" \
--gas-adjustment=1.5 \
--from=account_name \
--node=tcp://vm_ip:26657 \
--broadcast-mode block \
--trust-node false

stake_in_nund = (required) the amount of UND in nund you are self-delegating. You can use the undcli convert 1000 und nund command to convert UND to nund. E.g. 1000000000000nund. Note: do not enter more nund than you have in your wallet!

your_validator_public_key = (required) the public key output from the previous und tendermint show-validator command.

your_ev_moniker = (required) a publicly visible ID/tag for your Validator node.

your_website = (optional) website promoting your node

description = (optional) short description of your node

security_email = (optional) security contact for your organisation

chain_id = the network (e.g. UND-Mainchain-TestNet-v3) you are creating a validator on — this was obtained earlier in the guide via the jq command

account_name = the account self-delegating the UND, previously created/imported with the undcli keys add command

vm_ip = the IP address of your EC2 instance running the full node — you can get this from your AWS EC2 Instances console.

Commission Rates

Your commission rates can be set using the --commission-rate , --commission-max-change-rate and --commission-max-rate flags.

--commission-rate: The % commission you will earn from delegators’ rewards. Keeping this low can attract more delegators to your node.

--commission-max-rate: The maximum you will ever increase your commission rate to — you cannot raise commission above this value. Again, keeping this low can attract more delegators.

--commission-max-change-rate: The maximum you can change the commission-rate by in any one change request. For example, if your maximum change rate is 0.01, you can only make changes in 0.01 increments, so from 0.10 (10%) to 0.09 (9%).

The values for --commission-max-change-rate and --commission-max-rate flags cannot be changed after the create-validator command has been run.

Finally, the --min-self-delegation flag is the minimum amount of nund you are required to keep self-delegated to your validtor, meaning you must always have at least this amount self-delegated to your node.

For example:

./undcli tx staking create-validator \
--amount=1000000000000nund \
--pubkey=undvalconspub1zcjduepq6yq7drzefkavsrxhxk69cy63tj3r... \
--moniker="MyAwesomeNode" \
--website="https://my-node-site.com" \
--details="My node is awesome" \
--security-contact="security@my-node-site.com" \
--chain-id=UND-Mainchain-TestNet-v3 \
--commission-rate="0.05" \
--commission-max-rate="0.10" \
--commission-max-change-rate="0.01" \
--min-self-delegation="1" \
--gas="auto" \
--gas-prices="0.25nund" \
--gas-adjustment=1.5 \
--from=my_new_wallet \
--node=tcp://33.44.55.66:26657 \
--broadcast-mode block \
--trust-node false

Your validator node should now be registered and contributing to the network. To verify, on you local PC, run the following:

./undcli query staking validator \
$(undcli keys show account_name --bech=val -a) \
--chain-id=chain_id \
--node=tcp://vm_ip:26657

Replacing account_name, chain_id and vm_ip accordingly. Assuming you are going through this guide on TestNet, you should also see your node listed in https://explorer-testnet.unification.io/validators

Part 8: Final cleanup

Finally, it’s a good idea to close the RPC port (26657) on your validator node, leaving only the P2P port (26656) open so that it can communicate with other nodes. This can be done by deleting the firewall rule for the RPC port, and by reverting the RPC laddr configuration value in config.toml to the 127.0.0.1 IP address (which will restrict the node’s RPC access to localhost). Further interaction with the network can be done by spinning up a separate non-validator full node (on your local PC for example), and broadcasting transactions via that node instead.

Important: Do not alter the P2P port (26656) configuration and firewall rules. If you do, your validator node will not be able to communicate with its peers.

That’s it — you should now have a full Validator node up and running on a very basic AWS EC2 instance. Once again — Validator node operators are highly encouraged to explore more sophisticated architecture configurations to increase the security, reliability and availability of their Validator node.

Further commands relating to Validator Operators can be found in our “DevNews: Running a Full Node and Becoming a Validator” article.

Web: unification.com
Telegram: https://t.me/unificationfoundation
Twitter: https://twitter.com/UnificationUND
Gitter: https://gitter.im/unification-com

Tech issues related to und and undcli can be raised in the Github repo: https://github.com/unification-com/mainchain/issues

As always, feel free to track our overall progress — all of our public repos are available at https://github.com/unification-com

Paul Hodgson, Unification CTO