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Generic SCSI on a Linux Host Operating System

Using the SCSI Generic driver in Linux, VMware Workstation allows your guest operating system to operate generic SCSI devices within a virtual machine. The SCSI Generic driver sets up a mapping for each SCSI device in /dev. Each entry starts with sg (for the SCSI Generic driver) followed by a letter. For example, /dev/sga is the first generic SCSI device.

Each entry corresponds to a SCSI device, in the order specified in
/proc/scsi/scsi, from the lowest device ID on the lowest adapter to the highest device ID on the lowest adapter, and so on to the highest device ID on the highest adapter. Do not enter /dev/st0 or /dev/scd0.

Note: When setting up a generic SCSI device in the virtual machine settings editor, as described later in this section, you specify the device you wish to install in the virtual machine by typing its /dev/sg entry in the Connection field. You must be logged on as a user who has permissions to use the device.

Requirements

Generic SCSI requires version 2.1.36 of the SCSI Generic (sg.o) driver, which comes with kernel 2.2.14 and higher.

Avoiding Concurrent Access to a Generic SCSI Device

Under Linux some devices — specifically tape drives, disk drives and CD-ROM drives — already have a designated /dev entry (traditionally, st, sd and scd, respectively). When the SCSI Generic driver is installed, Linux also identifies these devices with corresponding sg entries in /dev — in addition to their traditional entries. VMware Workstation ensures that multiple programs are not using the same /dev/sg entry at the same time but cannot always ensure that multiple programs are not using the /dev/sg and the traditional /dev entry at the same time. It is important that you do not attempt to use the same device in both host and guest. This can cause unexpected behavior and may cause loss or corruption of data.

Permissions on a Generic SCSI Device

You must have read and write permissions on a given generic SCSI device in order to use the device within a virtual machine, even if the device is a read-only device such as a CD-ROM drive. These devices typically default to root-only permissions. Your administrator should create a group with access to read and write to these devices, then add the appropriate users to that group.

Device Support

In theory, generic SCSI is completely device independent, but VMware has discovered it is sensitive to the guest operating system, device class and specific SCSI hardware. We encourage you to try any SCSI hardware you want to use and report problems to VMware technical support.

Note: If you are using generic SCSI devices in a Windows 95, Windows 98 or Windows Me guest operating system and are experiencing problems with the devices, download the latest Mylex (BusLogic) BT/KT-958 compatible host bus adapter from www.lsilogic.com. This driver overrides what Windows chooses as the best driver, but it corrects known problems. To use SCSI devices in a Windows XP or Windows Server 2003 virtual machine, you need a special SCSI driver available from the download section of the VMware Web site at www.vmware.com/download.

Adding a Generic SCSI Device to a Virtual Machine

You can add generic SCSI devices to your virtual machine in the virtual machine settings editor. The virtual machine settings editor lets you map virtual SCSI devices to physical generic SCSI devices on the host.

When you set up a generic SCSI device, the virtual machine must be powered off.

1. Launch VMware Workstation and select the virtual machine. Make sure the virtual machine is powered off.

2. Choose VM > Settings. The virtual machine settings editor opens.

3. Click Add to start the Add Hardware Wizard. Select Generic SCSI Device, then click Next.

4. Choose the name of the physical device you want to use.

Then choose the virtual device node where you want this device to appear in the virtual machine.

A check box under Device status allows you to specify whether the device should be connected each time the virtual machine is powered on.

5. Click Finish to install the new device.

6. Click OK to save the configuration and close the virtual machine settings editor.

To remove this device, launch the virtual machine settings editor, select the generic SCSI device, then click Remove.

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