[Rainy Day]

I have a TDK CR-RW disc which refuses to erase. Disk Utility and the command line tools hdiutil and drutil all report the disc is not erasable. Disk Utility knows this is a CD-RW, but says the media is not erasable. Any way to erase/format this disc? I’ve tried using Leopard, Tiger, and even asked a friend to try to erase it on a PeeCee.

Here is the Disk Utility Info screen for the drive on my iMac with the disc inserted:

Code:
	Name : 	MATSHITA DVD-R UJ-875
	Type : 	Optical Device

	Partition Map Scheme : 	CD Partition Scheme
	Disk Identifier : 	disk1
	Device Name : 		MATSHITA DVD-R UJ-875 Media
	Connection Bus : 	ATA
	Connection Type : 	Internal
	Connection ID : 	Device 0
	Device Tree : 		/PCI0/PATA@1F,1/PRID@0/@0:0
	Total Capacity : 	172.4 MB (180,751,200 Bytes)
	Disk Number : 		1
	Partition Number : 	0
	Burn Support : 		Apple Shipping
	Entry Path : 		disk1
	Writes CD : 		Yes
	Writes DVD : 		Yes
	Media is present : 	Yes
	Media is busy : 	No
	Media Type : 		CD-RW
	Media is blank : 	No
	Media is appendable : 	No
	Media is overwritable : No
	Media is erasable : 	No
	Media is reserved : 	Yes

And here is the info screen for the disc itself:

Code:
	Name : 	OpenBSD 3.6
	Type : 	Volume

	Disk Identifier : 	disk1s0
	Mount Point : 		/Volumes/OpenBSD 3.6
	File System : 		ISO 9660 (Rockridge)
	Connection Bus : 	ATA
	Device Tree : 		IODeviceTree:/PCI0/PATA@1F,1/PRID@0
	Writable : 		No
	Capacity : 		150.1 MB (157,388,800 Bytes)
	Used : 			150.1 MB (157,384,704 Bytes)
	Number of Files : 	0
	Number of Folders : 	0
	Owners Enabled : 	No
	Can Turn Owners Off : 	No
	Can Be Formatted : 	No
	Bootable : 		No
	Supports Journaling : 	No
	Journaled : 		No
	Disk Number : 		1
	Partition Number : 	0

[0157988944]

this is an area I find really sketchy on the Mac. I have never once been able to use an already written cd-rw. It just tells me it isn't erasable.

[Art Vandelay]

I've never had a problem erasing CD-RWs on Macs.

If you're unable to erase this particular disc on multiple Macs and a PC, I'd give up on the disc and just use another one.

[Rainy Day]

If you're unable to erase this particular disc on multiple Macs and a PC, I'd give up on the disc and just use another one.

Well, that is perhaps the practical solution and i suppose it may come to that. But this has gotten under my skin (and is counter to my recycling-ethic).

In my Googling around (prior to posting) i found that – although rare – i am not alone in encountering this problem. There must have been something in the way this disc was written originally which caused this problem. I’m guessing that when it was written, those “Media is overwritable” and “Media is erasable” bits got set to “no,” and that is what is causing this problem. Even so, those are just bits on an erasable media, so there should be some way to reset them (if that is indeed the problem). I even tried running the command line tools hdiutil and drutil as root, but no luck.

That particular CD-RW was created from a .ISO image in the days of either Jaguar or Panther. If memory serves me correctly, i had to download a command line utility to burn it, as the native tools in those days couldn’t do .ISO. That may explain how those bits got set.

It also seems to me that a few years ago i read about a utility which just turned on the laser and moved the head across the disc, for reasons i can’t quite remember, but perhaps to solve problems like this? I thought perhaps someone might know of such a utility, or have another solution.

Still hoping for a solution here.

[Rainy Day]

Originally Posted by adamfishercox 

this is an area I find really sketchy on the Mac. I have never once been able to use an already written cd-rw. It just tells me it isn't erasable.

I generally have good luck erasing them in Disk Utility. If you have several discs to erase, drop into the terminal and issue a:

  drutil bulkerase quick

command. It will prompt for a disc, eject when done, and prompt for the next, etc. After it has ejected the last disc you wanted to erase, hit ^C. Important Safety Tip: Failure to exit this program with a ^C may result in unintentional CD-RW erasures because it will continue to run in the background, patiently waiting for the next disc insert. If you forget and insert another CD-RW you don’t wish to erase, well then you’re in for some pain.

For a full erase (which takes about a half hour), replace “quick” with “full”.

[Gavin]

Is the disk scratched or dirty?

Try cleaning it with dish soap.

[ghporter]

Have you tried to simply format it on your Mac?

[Rainy Day]

Originally Posted by Gavin 

Is the disk scratched or dirty?

No scratches, smudges, nor dirt. It is pristine.

Originally Posted by ghporter 

Have you tried to simply format it on your Mac?

I’m game, if you can tell me how to do that to a CD-RW. AFAIK, it can’t be done.

[ghporter]

My mistake, I was thinking of the "Erase" button. I've put both recorded and never-recorded CD-RWs in my own Matsushita (UJ 85J) drive and each has been recognized as erasable. This is quite odd.