In this chapter we looked at how each site could be configured. We started out by looking at site settings, and saw how they are separate by default, but can be shared to a limited extent. Then we moved on to modules and themes. We saw that in a multi-site configuration, modules and themes can be shared, or they can be stored in just one site. We also saw how even shared modules can have different configurations on different sites. We looked at themes, focusing on the complications that arise between the tight coupling of a site's database data and its theme files. We looked at using site-specific subthemes, focusing on how that could mitigate the problem.
In the next chapter we are going to turn our attention to site administration. There, we will see once again how sharing code, but not database data, can introduce some subtle challenges.