Configuring your SCSI Device

SCSI Required

In order to execute the store action, your CD-R or CD-RW drive must either be a SCSI device or must be configured to act like a SCSI device from the perspective of the cdrecord and mkisofs commands. Regardless of what kind of drive you have, make sure you know its SCSI address and its filesystem device name. The SCSI address will be used to write to media, and the device name will be used when Cedar Backup needs to mount the media (for instance, when a validation check must be run).

A true SCSI device will always have an address scsibus,target,lun, for instance 1,6,2. This should hold true on most UNIX-like systems including Linux and the various BSDs (although I do not have a BSD system to test with currently). The SCSI address represents the location of your writer device on the one or more SCSI buses that you have available on your system.

Linux Notes

On a Linux system, IDE writer devices often have a simulated SCSI address, which allows SCSI-based software to access the device through an IDE-to-SCSI interface. Under these circumstances, the first IDE writer device typically has an address 0,0,0. Newer Linux systems (kernel 2.6.x) can also be compiled with support for other kinds of CD drive interfaces. If your kernel supports it, you can address ATA or ATAPI drives without SCSI emulation by prepending an indicator to the simulated device address, for instance ATA:0,0,0 or ATAPI:0,0,0.

A discussion of how to configure your CD writer hardware is outside the scope of this document, but you may want to reference the Linux CDROM HOWTO (http://www.tldp.org/HOWTO/CDROM-HOWTO) or the ATA RAID HOWTO (http://www.tldp.org/HOWTO/ATA-RAID-HOWTO/index.html) for more information.

Mac OS X Notes

On a Mac OS X (darwin) system, things get strange. Apple has abandoned traditional SCSI device identifiers in favor of a system-wide resource id. So, on a Mac, your writer device will have a name something like IOCompactDiscServices (for a CD writer) or IODVDServices (for a DVD writer). If you have multiple drives, the second drive probably has a number appended, i.e. IODVDServices/2 for the second DVD writer. You can try to figure out what the name of your device is by grepping through the output of the command ioreg -l.[30]

Unfortunately, even if you can figure out what device to use, I can't really support the store action on this platform. In OS X, the “automount” function of the Finder interferes significantly with Cedar Backup's ability to mount and unmount media and write to the CD or DVD hardware. The Cedar Backup writer and image functionality does work on this platform, but the effort required to fight the operating system about who owns the media and the device makes it nearly impossible to execute the store action successfully.

If you are interested in some of my notes about what works and what doesn't on this platform, check out the documentation in the doc/osx directory in the source distribution.



[30] Thanks to the file README.macosX in the cdrtools-2.01+01a01 source tree for this information