PanLex: AWS instance retyping

Retyping methods

This document presupposes that you have already done the following:

• Configure a PostgreSQL cluster on an AWS instance
• Copy the database onto the instance

Now you have a running database server on AWS based on a particular instance type. If you wish to maintain that server except for its instance type, there are two methods from which to choose:

1. Stop the instance, change its type, and restart it.
2. Create an AMI from the existing instance, and create a new instance based on the desired type from the AMI.

Retyping procedure

Method 1 appears to be most efficient. Implement it as described below.

In the EC2 management console, stop the instance. This causes the following disruptions:

• Any existing SSH client is disconnected.
• The Elastic IP address becomes dissociated from the instance.

Once the instance is stopped, which typically takes about a minute, use the Change Instance Type menu item to change the instance type. Then undo the disruptions:

• Restart the instance with the Start menu item.
• Select the dissociated Elastic IP address and reassociate it with the instance.
• Connect by SSH as the “ubuntu” user to the instance.
• Make the /home/ubuntu/pgsql/custom directory the current directory.
• Reconfigure PostgreSQL and the kernel’s shared-memory parameters to conform to the new instance type with the command sudo ./pgresize.pl.

Connect to the PanLex Interface Server (if.panlex.org) and, with the privileges of the superuser, edit the file /etc/hosts to identify the database server’s new internal (private) IP address, as revealed by the EC2 Management Console.