I was playing around with the System Settings, and I foolishly increased the Zoom to 10.0 (normal being 1.0), after which the system crashed with an error saying:
A problem has occurred and the system can't recover. Please log out and try again.
How can I use the terminal to change the zoom settings back to normal?
The configuration settings can be changed using dconf. The following command would reset the magnifier settings:
dconf reset -f /org/gnome/desktop/a11y/magnifier/
This put all the magnifier settings back to default, and the magnification factor was back to 2.0.
In general, all the dconf settings can be found by running dconf dump /.