How can I prevent iOS devices from being mounted when I connect them?

Solution 1:

Configuring Automounting

To enable or disable automount open a terminal and type dconf-editor followed by the [Enter] key.

Browse to org.gnome.desktop.media-handling.

The automount key controls whether to automatically mount media. If set to true, then Nautilus will automatically mount media such as user-visible hard disks and removable media on start-up and media insertion.

There is another key org.gnome.desktop.media-handling.automount-open. This controls whether to automatically open a folder for automounted media.

If set to true, then Nautilus will automatically open a folder when media is automounted. This only applies to media where no known x-content/* type was detected; for media where a known x-content type is detected, the user configurable action will be taken instead. This can be configured as shown below.

Taken directly from the ubuntu help page.