I have a private blockchain, mined by one ec2 instance. When I restart the instance, significant part of the chain disappear with all transaction and contracts on it. How can I prevent this?
Please ensure you are using the same network ID and other parameters of the geth, while using the geth command, when you want to access your network over the console each time. If you alter the network ID or the datadir, it will not use the existing contents of the Blockchain