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Run a Validator (Alexander)

Note: This guide is for the Alexander testnet in the Polkadot repository on the v0.4 branch.

To be a good validator, you should

• Have DOTs to stake (basic requirement).
• Keep your node up to the latest version.
• Have enough knowledge of network security to create a secure network.

You should NOT run a validator if you have DOTs but do not have enough technical knowledge to set up a validator. If this is the case, you should nominate your DOTs to someone you trust.

Nominators still earn rewards. You can even nominate multiple validators. If you want to know more about nominators, please see here.

For this tutorial, we use Ubuntu 18.04 and will be running on the PoC-4 Alexander testnet. No matter what operating system you are using, setup should not be too different. There are a lot of VPS choices out there; feel free to pick the one you like.

Please make sure that you do NOT use this setup and configuration on Polkadot mainnet or Kusama. This guide simply walks you through step-by-step how to set up and run a validator node on the Alexander testnet. If you would like to run a validator on a non-testnet network, you must be EXTREMELY careful on some areas like key management, DDoS protection, and high availability.

Install Rust

curl https://sh.rustup.rs -sSf | sh
sudo apt install make clang pkg-config libssl-dev

The first command will fetch the latest version of Rust and install it. Execute the second command to install the required dependencies for Polkadot.

rustup update

If you have already installed Rust, run this command to check whether there is a new version available.

Install polkadot PoC-4

Until support for the one-line installer is back up for PoC-4, you will need to build polkadot from source.

You must use a specific version of nightly to install PoC-4. Follow the directions below:

rustup toolchain install nightly-2019-07-14
rustup default nightly-2019-07-14
rustup target add wasm32-unknown-unknown --toolchain nightly-2019-07-14

After switching to nightly-2019-07-14 as the default toolchain, the below instructions should work as written.

git clone https://github.com/paritytech/polkadot.git
# To update your node. Run from this step.
cd polkadot
cargo clean
git checkout v0.4
git pull origin v0.4
./scripts/init.sh
./scripts/build.sh
cargo install --path ./ --force

This may take a while depending on your hardware!

Synchronize Chain Data

Now you can start your Polkadot node. Start synchronizing the chain by executing the following command:

polkadot --chain alex

It will take at least a few hours.

You can check the current highest block via Telemetry or the PolkadotJS Block Explorer.

Create accounts

To be a validator, you will need three separate accounts for managing your funds, namely stash, controller, and session. If you want to know more about these accounts, please see here.

First, go to PolkadotJS => Account and click on the add account button.

To help easily identify your accounts later, make sure to use stash, controller, and session in the names of your accounts. A mnemonic seed phrase is given to you. You can save it in a safe place, offline, or you can choose to save your account using a JSON keyfile that will be generated automatically when clicking on Save. The password that is required to create an account will be used to sign any transaction made for each account. It will also be used to encrypt the JSON keyfile and will be required if you wish to restore your account using this file.

You need to generate three accounts:

1. Stash
2. Controller
3. Session

You can use either sr25519 or ed25519 for your Stash and Controller keys and must use Edwards (ed25519) for your Session key.

The mnemonic phrase for the Session account needs to be used later in this guide to validate. Make sure you save it safely.

Get Testnet DOTs Tokens

To continue the following steps, you are required to get some testnet DOTs for the stash and controller accounts in order to submit transactions and use these DOTs as stake. The session account doesn't need any DOTs. See the DOTs page for recommendations on getting testnet DOTs. Each of your accounts should have at least 150 milliDOTs to cover the existential deposit and transaction fees.

Bond DOTs

It is now time to set up our validator. We will do the following:

• Bond the DOTs of the stash account. These DOTs will be put at stake for the security of the network and can be slashed.
• Select the controller. This is the account that will decide when to start or stop validating.
• Select the session account. This is the account whose seed will be used to run the node.

First, go to the Staking section. Click on the "New stake" button.

• Stash account - Select your stash account, we will bond 100 milliDOTs, make sure it has enough funds.
• Controller account - Select the controller account created earlier.
• Value bonded - Enter how many DOTs from the stash account you want to bond/stake. You can top up this amount and bond more DOTs later, however, withdrawing any bonded amount requires the bonding duration period to be over (several months at the time of writing).
• Payment destination - Select where the rewards get sent. More info here.

Once everything is filled properly, click Bond and sign the transaction (with your stash account).

Set the Session Key

You should now see a new card with all your accounts. The bonded amount on the right corresponds to the funds bonded by the stash account.

Click on Set Session Key. Select the session account created previously and click on Set Session Key.

Validate

You should now be able to see both Validate and Nominate buttons for your Session key.

At this point, and before validating, you should make sure your node is synced. Open your terminal and run your validator with the seed or the mnemonic from the session account, e.g:

polkadot --chain alex --validator --key="SESSION_ACCOUNT_SEED" --name NAME_ON_TELEMETRY

Make sure that the address generated from the seed corresponds to your session account's address. Don't worry if the last characters diverge, it's just the checksum that has recently changed.

To verify that your node is live and in sync, head to Telemetry, after a few seconds, your node's information will be shown.

If everything looks good, go ahead and click on Validate in Polkadot UI.

• Unstake Threshold - Set how often you want to be reported offline (and slashed) before being removed from the validator set. A higher value will allow you to be offline more times before being slashed, but you will be slashed more severely.
• Reward Commission - Select how much of the reward you will keep; the rest will be shared among you and your nominators.

Click Validate.

Go to the Staking tab, you should see a list of active validators out there. At the top of the page, it shows how many validator slots are available and how many nodes intend to be a validator.

Your node will be shown on the next up queue. In the next era (up to 1 hour), if you have enough backing, your node will become an active validator.

Congratulations!

If you want to run your validator as a systemd process, see the short guide here.

Notice: As mainnet gets closer, you can expect more slots to be available for testing.

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