[Q] How do you set the default install location without adb?

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http://forum.xda-developers.com – I am working on a rom, and looking to set the default install location of the rom. I know I've seen it somewhere before, but can't recall where. So, I'm asking the collective minds of XDA. Somewhere in the rom, the default install location value is stored (typically 0 or 2). Where is this location? Is it in a settings database or is it something easily modified? At first I thought it might be a build.prop attribute, but I don't believe it is. And I will need to set it in the rom itself, not by the end user via adb, if I didn't make that clear. (HowTos)