Install a VirtualBox with a commandline attached iso

I have created a VirtualBox, that has not yet an OS installed. If I attach a bootable iso file with OS installer via GUI->settings->network and start the box per gui or per VBoxManage, the OS is properly installed from the iso file. If I attach the same iso with VBoxManage storageattach the installation fails with 'No bootable medium found!' error when stated via GUI, or with:

VBoxManage: error: The virtual machine 'BAD' has terminated unexpectedly during startup because of signal 6
VBoxManage: error: Details: code NS_ERROR_FAILURE (0x80004005), component MachineWrap, interface IMachine

when started with VBoxManage startvm. The output of 'VBoxManage showvminfo' for the dvd device is identical in both cases. How is the correct way to install an OS with command line?