The Inno Setup install parameters that are required for silent installation.

/SILENT Runs the installer in silent mode (The progress window is displayed)
/VERYSILENTVery silent mode. No windows are displayed.
/SUPPRESSMSGBOXESSuppress message boxes. Only has an effect when combined with ‘/SILENT’ and ‘/VERYSILENT’.
/NOCANCELDisables cancelling the installation process.
/NORESTARTPrevents installer from restarting the system even if it’s necessary.
/DIR=”x:\dirname”Overrides the default install directory.

Example

Silently install the program, prevent restarting the system.

setup.exe /VERYSILENT /SUPPRESSMSGBOXES /NORESTART