hdiutil command cannot work properly with Catalina macOS

Help - how can I get Write permission to the root?

That is no longer possible. Constraining potential solutions to that will be futile.

For productive solutions I believe you will need to provide the complete hdiutil command you had used in the past, as well as any subsequent actions that resulted in a readable disc.

Consider simpler causes, such as an optical drive that isn't working properly — burning or reading, or defective / degraded optical media.

You need to select the correct path to your DMG file you wish to "burn" or manipulate. The easiest method is just to type your Terminal command, then drag & drop the file from the Finder onto the open Terminal window so the proper path is automatically filled in for you.

Otherwise you need to learn more about the command line if you wish to use Terminal commands. You should never blindly use any Terminal commands without understanding them since even a simple typographical error could result in unexpected results and even catastrophe such as permanently deleting your files. I suggest you begin with this six part tutorial.....while it is using the Bash shell, most of the items should also pertain to Zsh shell used by later versions of macOS as the default (it is easy to switch between them and is a personal preference).

https://scriptingosx.com/2017/07/first-steps-in-terminal/

Edit: It also sounds like you are following directions from someone who doesn't understand the command line either. So proceed with caution.

I highly recommend to make sure you have a good current backup before doing anything with the Terminal command line so you can restore the system if you make a catastrophic mistake.

LorInCalif wrote:

See also my reply to John Galt.

Are you suggesting that it might work to place the source dmg at the root of a non-system drive and send that path to hdiutil ? I will try it. /Volumes/whatever/source etc.

It doesn't matter where the file is located as long as it is some where that you have permissions to save/create it. It would be best to keep it in your home user folder like you do all other files/projects you create with other apps & methods.

You just need to learn how to use the command line properly to access the files.

FYI, I would not recommend creating any folders under "/Volumes" as that location is meant to be the mount point for externally mounted drives and DMG archive images. When you double-click to open a DMG archive or use "hdiutil" to manually attach the DMG archive, then macOS will automatically place their mount points under "/Volumes". macOS will automatically create the proper folder under "/Volumes" and also automatically delete the folder used for the mount point once you eject the drive/volume or "detach" it using "hdiutil".

I understand you want to use hdiutil to create a mountable disk image with which to burn a CD-ROM that will mount automatically, upon inserting it in the optical drive. Is that correct?

If so I understand, and the fact you did it successfully in the past implies it should still be possible, bearing in mind writing to / (the root directory of a startup disk) is no longer an option.

If all that is correct then try your proposed solution:

Are you suggesting that it might work to place the source dmg at the root of a non-system drive and send that path to hdiutil ? I will try it. /Volumes/whatever/source etc.

I have never attempted to do that without third party utilities (perhaps it was Roxio Toast; I don't recall) and my initial impression was that macOS and its predecessors lacked a native ability to do that. But you did it before... so try it. I can attempt some solutions myself but they will be time-consuming. Let us know if your technique works.

By way of clarification there is no secret to burning a CD-ROM that can be mounted. If you want to have something auto-launch, implying merely inserting the disk results in invoking an installation procedure (for example) that's a separate challenge. So I need to clarify that before going down that road.

You're welcome Lor. Glad to help.

Apple's unilateral changes to their systems can occur over a period of years (the transition from 16 to 32 to 64 bit hardware and software for example), or months (AppleTalk), or in this case, essentially overnight. One day in August 2011 an edict came down from on high and just like that, CDs and DVDs were abandoned as though they never existed. Those of us accustomed to Apple's ways saw the writing on the wall and learned to abandon them just as quickly. So it was then I forgot about Roxio Toast or any corresponding features in Disk Utility.

For someone with such an extensive background it must bemuse you to observe how Apple's customers have grown to expect literal magic from their products. For the most part they just work, with no appreciation for how seamlessly integrated they are to fulfilling whatever needs (demands?) they may have. They are no longer "computers" in the traditional sense and I stopped associating that term with Macs years ago. They're Macs, (which are inexorably becoming iPhones anyway) and if you want a "computer" today you have to build one yourself.

In creating the original Macintosh, Apple's founders sought to create an "information appliance". They succeeded.

What exactly are you trying to achieve?

You cannot modify the root level of the system drive, /

You can modify other drives, and that does not require messing with /

Please clarify.