Device ens3 doesn't exist and so env var PRIVATE_IP is not set.

[jdeprin]

see https://github.com/circleci/enterprise-setup/blob/master/templates/services_user_data.tpl#L20

ens3 is not always a valid device name. Without this env var set the install fails. Since this is aws specific you can use the metadata url to gain this information:

export PRIVATE_IP="$(curl http://169.254.169.254/latest/meta-data/local-ipv4)"

[MikeyYeahYeah]

It is definitely a good idea to put some logic around determining the private IP address. Your method is the idea way in AWS envs. I will try and create a PR soon that addresses this.