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I'm trying to compile a FreeBSD kernel and make it as light as possible. I'm struggling with the configurations on the bus, especially the SCSI Controllers part. there are many modules e.g: ahc, ahd , ... and I don't know how to find out which ones I need.When I run dmesg I get two entries for buses:

  1. ACPI PCI Bus
  2. ISA Bus

But I also get something about SCSI in :

cd0: Removable CD-ROM SCSI-0 device

I'm Running FreeBSD 9.3.0 on a VirtualBox VM on an i686 pc.

should I keep the SCSI Controller Modules? If yes then which ones?

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Virtualbox allows to configure two types of SCSI controllers, one being LSILOGIC the other Buslogic compatible.

Those should be supported by the bt(4) and mpt(4) drivers. You can remove all other SCSI controllers

If you use IDE/SATA controllers you can remove all SCSI drivers.

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I'm using an IDE Controller. But what about the line about SCSI device I mentioned above? – user2268997 Apr 1 '15 at 17:59
This is because of the ATA_CAM option. I agree the message is a bit misleading – arved Apr 2 '15 at 8:12

You need to include the drivers for the hardware that you've configured in your virtual machine. To keep things lightweight, put all the disks and CD devices on the same controller. Check the release notes for the list of drivers and the hardware they support. For example, if you choose a SATA AHCI controller (less hassle than IDE with its very limited number of devices or SCSI with its multiple host drivers), include the ahci driver.

I don't think VirtualBox emulates anything connected to an ISA bus. PCI is where it's at on a PC that's less than 20 or so years old.

ACPI is power management. I don't know to what extent you'll get mileage out of it in a VM.

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