AWS Minecraft Utilities

This repo currently contains utilities to run a minecraft server on EC2. For a server that only turns on a few hours a month, this is very cost-effective.

Maybe one day I will make this entirely automatic and configurable. Until then, I hope some of these pieces are useful to you.

Autoupdate DNS

Unless you pay extra for a static Elastic IP Address your EC2 server will be assigned a new public IP each time you start it. Use this script to tell Route53 about the new IP every time the server boots so people can join the game using DNS.

1. Copy the update_dns.sh script to your server.
2. Run crontab -e to edit your cron
3. Put @reboot /path/to/update_dns.sh > ~/log 2>&1

The script assumes you have run aws configure to set up access keys. I recommend creating an IAM role that only has permissions to update DNS.

Auto startup

Copy minecraft.init.d to /etc/init.d/minecraft.

Website to let your friends turn on the server

Create a IAM User for the website

Set up an IAM user with the policy below. That policy will allow that user to start instances with the use=minecraft tag if they are a t2 instance. It will also allow the user to modify attributes of any instance. Unfortunately there is no way to lock this down any further, which is the reason the StartInstances permission is locked down so tightly.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "ec2:StartInstances",
            "Resource": [ "arn:aws:ec2:*:700044736775:instance/*" ],
            "Condition": {
                "StringEquals": {
                    "ec2:InstanceType": [ "t2.nano", "t2.micro", "t2.small", "t2.medium", "t2.large" ],
                    "ec2:ResourceTag/use": "minecraft"
                }
            }
        },
        {
            "Effect": "Allow",
            "Action": "ec2:ModifyInstanceAttribute",
            "Resource": [ "*" ]
        }
    ]
}

Create a lambda function so the website can get the credentials

Use the instructions here to set up a lambda function that returns the credentials for the user created above.

Allow node to bind to privileged ports

Run this command to allow node to bind to ports < 1024:

sudo setcap cap_net_bind_service=+ep `readlink -f \`which node\``