How do I configure an AWS EC2 instance so the license file remains valid?

A Gurobi license file setup on an AWS EC2 instance will remain valid if the EC2 instance is simply stopped and restarted. However, without additional configuration, a Gurobi license file may become invalid after the EC2 instance is terminated. 

Gurobi license files are tied to specific hardware/software components of the host machine. These components normally change when EC2 instances are terminated and relaunched.

For Linux instances

On Linux, a Gurobi license file depends on the primary network interface, which may change when starting a new AWS EC2 instance. To prevent this, assign an Elastic Network Interface (ENI) to the EC2 instance and bind the Gurobi license to this new network adapter. With an ENI, the license file will continue to work, since the network interface persists for the machine running Gurobi.

Assigning a license file to the primary ENI

To assign a Gurobi license file to an ENI attached as the primary network interface, perform the following steps:

1. Create a new ENI.
2. Attach the ENI to your EC2 instance, assigning the ENI as the primary network adapter.
3. Start your EC2 instance.
4. Log in to your account on the Gurobi website and navigate to Downloads & Licenses->Your Gurobi Licenses. Click the appropriate license ID, then follow the instructions to download the license file onto the EC2 instance using grbgetkey.

Assigning a license key to a secondary ENI

Assigning a Gurobi license file to an ENI attached as a secondary network interface is a more complicated process because grbgetkey only considers the primary network interface. It can be done by performing the following steps:

1. Create a new ENI.
2. Attach the ENI to your AWS EC2 instance, assigning the ENI as the secondary network adapter.
3. Start your AWS EC2 instance.
4. Determine the hostname and host ID of the ENI.
   • Hostname: Run hostname when logged in to the machine or assign a custom hostname
   • Host ID: These are the last eight hexadecimal digits of the MAC address. In the image below, the host ID is 8de5be82:
     
5. Log in to your account on the Gurobi website and navigate to Downloads & Licenses->Your Gurobi Licenses. Click the appropriate license ID, then download the license file using the manual process at the bottom of the webpage:
   
6. Copy the license file to the EC2 machine.