A CD-R/RW/DVD-R/RW device is not a normal random-access writable device. You cannot simply write bits to it the same way you write bits to an HDD or SSD.
The special burning programs (e.g. wodim) first send commands to the drive to find out what kind of disc is in there, and once that's known, they send special commands to prepare the drive for writing, then sends the data in a particular format via a special
interface, then finally sends the commands to the drive to have it write out the correct track padding and postamble.
There are several burning modes you can use to create a disc from an ISO file; normally it doesn't matter very much, you should be able to go with whatever your drive or burning program uses by default.
If wodim et al complain the disc in the drive is read-only, that's because it is. Or at least your drive thinks it is.
Make sure you do in fact have a drive capable of writing the size of ISO onto the type of disc you have, and if that all checks out, just throw the first disc away and use a new one.
There are hundreds, probably thousands, of guides to burning discs on the Internet - even at the end of the physical media era, it could still be pretty complicated depending on what you were burning in what format to what kind of media using what kind of drive
with what program. You're in for a bunch of reading to figure this all out, I'm afraid.
-Adam
From: Tait Palsson <votetaitpalsson@protonmail.com>
Sent: Monday, March 23, 2026 5:06:58 PM
To: roundtable@muug.ca <roundtable@muug.ca>
Subject: [RndTbl] Roundtable
Hello MUUG Roundtable,
Is it just me or is it impossible to burn a .iso to an optical disc?
I have tried with dd, various iso writers on various distributions but these either grey out or do not list the target device, and with multiple pieces of hardware. I am
always met with an error that the media is read-only when the disc drive is read and write. I also tried /dev/sr0 and its alias /dev/cdrom but nothing different happened.
An internet search tells me that special software like wodim, growisofs, or Brasero could be needed. Why and is this just me?
If dd did work I imagine that I could use bs= to bring down the write speed and improve accuracy.
Sincerely,
Tait
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