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DeFi, NFTs, and Metaverse’s first Cosmos EVM chain, the Cronos chain has been buzzing the Cryptoverse since its promising launch. The cross-ecosystem interoperating blockchain network, Cronos, is affordable, with enhanced throughput and speedy finality.

Geared towards scaling the DeFi and Web3 communities, Cronos chain offers swift porting of apps and cryptocurrencies across chains. Cronos chain is a Cosmos SDK-built chain that operates swiftly with IBC across various Cosmos ecosystem chains.

dApp building on the Cronos mainnet Beta cronosmainnet_25-1 requires developing a fully-functional node for running events and executing queries. Running Cronos Mainnet Beta nodes has the following machine system prerequisites: 4-core, x86_64 architecture processor with 16 GB RAM and a storage space of 1 TB.

Preparing an AWS EC2 Machine with Flexible Storage

After signing-in to the AWS Console, select Amazon Linux 2 Kernel 5 64-bit (x86) as the machine to be used. A t2 or t3 machine having 4 cores or a x86_64 architecture processor with 16 GB of RAM would suffice. Ensure having enough provisions made to oversee the /dev/sdb (root and EBS) volume as later on increasing the elastic storage could be required.

Then decide on a Name Tag to easily identify the said instance in the AWS Management Console (MC). Lastly, prepare a Security Group (SG) with default settings selected.

A private key pair (.pem file) must then be created, downloaded and saved in your computer device (in an easily accessible directory—for instance ~/cronosdir).


Link with EC2 VM a Dedicated IP Address

Access the ‘Allocate Elastic IP address’ button on the right top corner of the EC2 MC. Then click on the ‘Actions’ button on its left for associating it with the EC2 VM. 


Port 8545 for RPC-JSON Queries

Sending RPC-JSON queries requires opening port 8545 in the EC2 MC. You can do it via accessing the Instances button, and then the security group associated with your VM. Select ‘Edit Inbound Rules’ option given under the Security Groups menu, via selecting the SG linked with your VM. To connect to the AWS EC2 instance, use these commands in a Terminal window.


AWS EC2 Instance Connection

Initiate the following commands in a ~/cronosdir directory Terminal window:

Fix the permissions of the key pair file

chmod 400 cronos-01.pem

Connect to the EC2 virtual machine

ssh -i "cronos-01.pem" ec2-user@elastic_ip_associated_with_vm

Once connected, update libraries and install missing ones

sudo yum update

sudo yum install jq


Extra Storage Mounting for the Blockchain Data

Keeping the EC2 virtual machine connected, initiate these commands in the Terminal:

List available storage volumes – Here you can retrieve the File system name of the 1000 GB volume, which should be something like /dev/nvme1n1

lsblk

List UUIDs of available storage volumes, Here you can retrieve the UUID of the 1000 GB volume, which  should be something like 0bcd4d37-a271-4b2c-a475-a2bdb05f5f0d

sudo blkid

Mount the 1000 GB volume and associate it with /cronos directory, Replace /dev/nvme1n1 and 0bcd4d37-a271-4b2c-a475-a2bdb05f5f0d by the correct values in the following commands

sudo mkfs -t xfs /dev/nvme1n1

sudo mkdir /cronos

sudo mount /dev/nvme1n1 /cronos

Let’s edit the file /etc/fstab

sudo vim /etc/fstab

With your terminal having the /etc/fstab file opened, insert the following row below the file:

UUID=3a5c2d89-be70-4d9b-8597-e20af21db901  /cronos  xfs  defaults,nofail  0  2

Alter the /cronos directory permissions to enable its writability and executability via the Cronos client:


Installing the Cronos Mainnet Binary Client (cronosd)

While still connected to the VM in your terminal, go to the user directory 

cd ~/

Replace the URL below by the latest URL given in the official documentation at https://cronos.crypto.org/docs/getting-started/cronos-mainnet.html#step-1-get-the-cronos-mainnet-beta-binary

curl -LOJ <https://github.com/crypto-org-chain/cronos/releases/download/v0.6.1/cronos_0.6.1_Linux_x86_64.tar.gz&gt;

Replace the file name below by the correct file name if needed

tar -zxvf cronos_0.6.1_Linux_x86_64.tar.gz

We check that cronosd has been installed to the ~/bin/cronosd directory, this command should return the version number ./bin/cronosd version, We move cronosd to the main bin directory, then check that cronosd can be called from anywhere. The last command should return the version number.

sudo mv ./bin/cronosd /bin
cronosd version


Initializing Cronosd

Start cronos d’s Initialization.

Replace [moniker] by the name that we want to give to our node. Replace cronosmainnet_25-1 by the correct value if it has changed. Note that we use the –home option to make sure that the cronos data is stored on the mounted 1000 GB drive, not on the root volume.

cronosd init [moniker] --chain-id cronosmainnet_25-1 --home /cronos/.cronos


Archive node configuration of cronosd

Change the node’s configuration to make sure safe storage of blocks and transactions. First un-toggle fast sync, then deactivate pruning.

Edit the /cronos/.cronos/config/config.toml file

vim /cronos/.cronos/config/config.toml

fast_sync should be changed to false and saved in config.toml,

fast_sync = false

Edit app.toml.

vim /cronos/.cronos/config/app.toml

Convert pruning from default to nothing in app.toml and save it.

pruning = "nothing"


Keep cronos’ configuration continue

The genesis file must be downloaded and saved in the following directory; /cronos/.cronos/config/

curl <https://raw.githubusercontent.com/crypto-org-chain/cronos-mainnet/master/cronosmainnet_25-1/genesis.json&gt; > /cronos/.cronos/config/genesis.json

Initiate the following command for ending the configuration. Verify sha256sum checksum of the downloaded genesis.json. You should see OK! if the sha256sum checksum matches.

if [[ $(sha256sum ~/.cronos/config/genesis.json | awk '{print $1}') = "58f17545056267f57a2d95f4c9c00ac1d689a580e220c5d4de96570fbbc832e1" ]]; then echo "OK"; else echo "MISMATCHED"; fi;

In cronos/.cronos/config/app.toml, update minimum gas price

if [[ $(sha256sum /cronos/.cronos/config/genesis.json | awk '{print $1}') = "58f17545056267f57a2d95f4c9c00ac1d689a580e220c5d4de96570fbbc832e1" ]]; then echo "OK"; else echo "MISMATCHED"; fi;

sed -i.bak -E 's#^(minimum-gas-prices[[:space:]]+=[[:space:]]+).*$#\\1"5000000000000basecro"#' /cronos/.cronos/config/app.toml

For network configuration, in cronos/.cronos/config/config.toml, to modify the configurations of persistent_peers, we create_empty_blocks_interval and timeout_commit

sed -i.bak -E 's#^(seeds[[:space:]]+=[[:space:]]+).*$#\\1"0d5cf1394a1cfde28dc8f023567222abc0f47534@cronos-seed-0.crypto.org:26656,3032073adc06d710dd512240281637c1bd0c8a7b@cronos-seed-1.crypto.org:26656,04f43116b4c6c70054d9c2b7485383df5b1ed1da@cronos-seed-2.crypto.org:26656"#' /cronos/.cronos/config/config.toml

sed -i.bak -E 's#^(create_empty_blocks_interval[[:space:]]+=[[:space:]]+).*$#\\1"5s"#' /cronos/.cronos/config/config.toml

sed -i.bak -E 's#^(timeout_commit[[:space:]]+=[[:space:]]+).*$#\\1"5s"#' /cronos/.cronos/config/config.toml

Generate keys and initiate the below mentioned command. Select a password and save it. A mnenomic phrase will be given which must be saved safely as well.

cronosd keys add Default


Cronosd client initialization

At this point, creating a cronosd service is required to enable starting the cronosd client upon restarting the virtual machine.

curl -s <https://raw.githubusercontent.com/crypto-org-chain/cronos-docs/master/systemd/create-service.sh&gt; -o create-service.sh && curl -s <https://raw.githubusercontent.com/crypto-org-chain/cronos-docs/master/systemd/cronosd.service.template&gt; -o cronosd.service.template

chmod +x ./create-service.sh && ./create-service.sh

Edit the /etc/systemd/system/cronosd.service file

sudo vim /etc/systemd/system/cronosd.service

The ExecStart line must be changed to as follows and saved:

ExecStart=/usr/bin/cronosd start --home /cronos/.cronos

After it, do the following:

sudo systemctl daemon-reload

sudo systemctl start cronosd

Check node’s sync progress (in number of blocks). You can compare the number of blocks to the one shown in the Cronos block explorer at the URL https://cronos.crypto.org/explorer/

cronosd status 2>&1 | jq '.SyncInfo.latest_block_height'

Stop cronosd service

sudo systemctl stop cronosd


Query your node remotely

After full node’s syncing completion, sending any JSON-RPC query to the node in a remote manner becomes possible via the standard Ethereum request formats.

Happy dApps building to you!

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