I'm upgrading from 18.104.22.168 to the latest (22.214.171.124) and I seek to have as little template customization as possible.
Following a guide that made the most sense to me, I performed a mysqldump of production 126.96.36.199 site and restored to local dev server with same db name, user, etc. I got the latest Magento code. I navigated to the internal webserver and went through the install procedure and got the generic store view with the dog we all know. Surprisingly, everything seemed to go well: current orders showed up, the same nagging messages are in admin, etc etc.
I read Alan Strom's parent/child theme blog, went through the steps and got the "blank" or "broken css" look he gets but then I couldn't get the "modern" theme to show up:
I did add a theme directory and change from the previous a304 template master theme to this name. There have been no extensions or template files copied.
My goal is the most plain and simple 2 column layout with the minimum number of files. I let a dev friend talk me into modding the template when we first adopted Magento in 2011 and that is the biggest mistake ever. Even with github version control, upgrading the site isn't fun.
Any thoughts on where to start digging around?