This information is included in help too. These are the parameters accepted by the FBackup installer via command line:
/SILENT, /VERYSILENT

Instructs Setup to be silent or very silent. When Setup is silent the wizard and the background window are not displayed but the installation progress window is. When a setup is very silent this installation progress window is not displayed. Everything else is normal, so for example error messages during installation are displayed.

If a restart is necessary and the /NORESTART command isn't used (see below) and Setup is silent, it will display a Reboot now? message box. If it's very silent it will reboot without asking.
/SUPPRESSMSGBOXES

Instructs Setup to suppress message boxes. Only has an effect when combined with /SILENT and /VERYSILENT.
/NOCANCEL

Prevents the user from canceling during the installation process, by disabling the Cancel button and ignoring clicks on the Close button. Useful along with /SILENT or /VERYSILENT.
/NORESTART

Instructs Setup not to reboot even if it's necessary.
/QUIET

Instructs Setup to be quiet. When a setup is quiet, there is no user interaction and the installation progress window is not displayed. However the error messages during installation are displayed.
/PASSIVE

Instructs Setup to be quiet. When Setup is quiet, the wizard and the background window are not displayed but the installation progress window is. Everything else is normal so for example error messages during installation are displayed. If a restart is necessary and the /NORESTART command isn't used (see below) and Setup is quiet, it will display a "Reboot now?" message box.
/q[n|b|r|f] - Sets user interface level

n - No user interface

b - Basic user interface

r - Reduced user interface

f - Full user interface (default)
/DIR="installation path"

Overrides the default directory name displayed on the Select Destination Location wizard page. A fully qualified pathname must be specified.