The default file explorer application used in Ubuntu is Nautilus. To set Nemo as the default file manager I first installed exo-utils:
$ sudo apt-get install exo-utils
Next, I opened the
exo-preferred-applications from the shell and in Utilities > File manager section set Nemo as my file manager:
The changes are applied immediately. However, I noticed that xdg-open stopped working. Any application that used it to open files, like Chrome for example, would just open Nemo with that file highlighted.
It turns out that the problem is exo-utils. It has been filed as a bug.
If you face this problem, remove exo-utils package:
$ sudo apt-get purge exo-utils
Restart and the default behavior of xdg-open should be back.
Note: The right method to set Nemo as default file manager is here.
Tried with: Ubuntu 14.04