I've been setting up CentOS-7-based VFX Platform docker images there: https://github.com/AnimalLogic/docker-usd/blob/master/linux/centos7/vfx-lite-2018/Dockerfile

It's actually quite a nice way to go, I don't know how packer works exactly but these docker files can be reused to setup everything the right way for a centos-7 based build.

Cheers,

Aloys
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