I have an application that is being distributed as two RPMs. One of them contains data files shared by all versions of the app, and the other contains files for the specific version being installed. In order for the application to work correctly, the version-specific files need to be installed in a subdirectory of the directory containing the version-shared files.

Everything seems to work fine if I make the shared package a dependency of the version package and hard-code the install directory. Problem is, I want to make the application relocatable. That is, I want to let the user set a prefix for the shared RPM and then have the version RPM automatically install into the same directory. Is there any way to do this?

Looks like it can be done. Go to the RedHat website and download the book Maximun RPM https://www.redhat.com/docs/books/max-rpm/index.html.

See chapter 15 on making a relocatable rpm. It looks like you would have to make the second rpm query the first to find the DEFAULT_PREFIX for installing the first package, then make the second install to the same default location.

PS: it's a big book; 700+ pages.

Thanks. DEFAULTPREFIX isn't quite what I wanted, but that got me to look at the querytags list, and it looks like INSTALLPREFIX will work.

I'm still having some trouble, though. I need to refer to this prefix in both the install and files sections of my spec file, but each section is treated as a separate script and I don't know of any way to share variables between them. Is there a way to set a global variable at runtime?

Refering back to the book Maximum RPM, see chapter 13 Tags: Data Definitions, the section about Directory-related tags. The --prefix option can be given at install time, as well as in the .spec file.

Write your INSTALL or README to include instructions to the prospective user about using the --prefix option at instal time.

Well, okay. I'd really hoped to automate this, but I guess I can just make the user do it. Thanks.