How do you configure Tracker search indexing tool?

Ubuntu 20.04

Folders to include in scan can be specified in:

Settings → Search → Search Locations (button on top bar)

Also you can exclude a specific folder and its subfolders by creating an empty .trackerignore file in the folder.

The command tracker-preferences is from the tracker-gui package, but the package is not available for Ubuntu 17.10 Artful Aardvark. In fact in Artful, tracker is not installed by default.

For other supported versions (Trust and Xenial) You may have to install the tracker-gui package first in order to run tracker-preferences.

Update for Ubuntu 20.04

In Ubuntu 20.04 and 19.10, the package tracker-preferences is not available. To configure what folders and files Tracker indexes, as well as other settings such as indexing while on battery:

• Install dconf Editor, either in Terminal via sudo apt install -y dconf-editor or in Ubuntu Software.
• Run dconf Editor (search for it in the desktop search).
• In dconf Editor, browse to org > freedesktop > Tracker > Miner > Files
• Carefully modify the settings for Tracker
• When you are done, simply close dconf Editor

Here is a screenshot of dconf Editor:

This can all me done via the command line as well via gsettings. To view the available settings, use:

gsettings list-recursively org.freedesktop.Tracker.Miner.Files

For more information on Tracker, read the useful but hard-to-find Tracker FAQ.