EC2 instance unreachable when changing instance type

If EC2 instance has not yet been switched to another type and is still accessible, verify that cloud-netconfig-ec2 package is installed by running:

sudo rpm -qa | grep cloud-netconfig-ec2

If the package is not installed, install it by running:

sudo zypper install -y cloud-netconfig-ec2

If EC2 instance has already been switched to another instance type and is no longer accessible, follow steps 1-7 from Amazon document https://aws.amazon.com/premiumsupport/knowledge-center/ec2-instance-boot-issues/
From chroot, install the cloud-netconfig-ec2 package:

sudo zypper install -y cloud-netconfig-ec2

Then follow steps 13-15 from Amazon document https://aws.amazon.com/premiumsupport/knowledge-center/ec2-instance-boot-issues/

Without cloud-netconfig-ec2 package installed, when instance boots, udev will create a persistent net config rule (/etc/udev/rules.d/70-persistent-net.rules) which will break the instance's connectivity if the instance type is changed.  The instance will become unreachable because instead of activating eth0 as expected, udev will detect the network interface as a new device and add it as eth1. Due to a lack of configuration of eth1, the interface won't be configured.

cloud-netconfig-ec2 disables persistent interface names to avoid /etc/udev/rules.d/70-persistent-net.rules from being created. Therefore cloud-netconfig-ec2 must be installed to prevent network interface activation issues when changing EC2 instance type.

This issue has been identified when moving from:
Nitro to Xen
Xen to Nitro
Nitro to Bare Metal
Bare Metal to Xen
Bare Metal to Nitro