Generic SCSI on a Linux Host Operating System

Using the SCSI Generic driver in Linux, GSX Server 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.

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. GSX Server 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.

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.