How to set bash as default shell?

When I adb into a device with Cyanogenmod, I'm presented with a nice bash shell, color prompt, and bashrc. I don't see a symlink from /system/xbin/bash to /system/bin/sh. How do they set the default shell to bash instead of sh? I looked through rc files, but didn't find anything. I'd like to do the same on my Android build, which isn't Cyanogenmod. **Update** After re-installing from scratch with CM7, I'm taken to sh instead of bash. Now the question is how to set bash as default.