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I have already read most of the questions and answers relating to this issue, which is supposed to be simple, but I still can't do it.

The unmount step goes ok:

sudo diskutil unmountDisk /dev/disk4
Unmount of all volumes on disk4 was successful

but the dd command exits with error:

sudo dd if=/dev/disk4 of=mydisk.iso
dd: /dev/disk4: Permission denied
10656+0 records in
10656+0 records out
5455872 bytes transferred in 2.834248 secs (1924980 bytes/sec)

I can't understand the error dd: /dev/disk4: Permission denied. I can't find anything wrong with /dev/disk4, the DVD plays rather well and I can watch the movie.

ls -l /dev/disk4
br-xr-----  1 erothe  operator  0x1000014 Nov 27 18:27 /dev/disk4

This steps are based on Mac OS X: Best Way to Make an ISO from a CD or DVD.

Notes:

  1. if I use diskutil unmount on step 1, the result does not change;
  2. I have chmod u+x /dev/disk4 just in case some witches were flying around;
  3. the dd command creates a file with 5MB (DVD has 700MB).
Giacomo1968
  • 55,001
Eduardo
  • 123
  • Does it have copy protection, perhaps? – ChanganAuto Nov 27 '23 at 18:44
  • “… the DVD plays rather well and I can watch the movie.” The DVD most likely has copy protection. – Giacomo1968 Nov 27 '23 at 18:46
  • Usually and for most people it is easier to just download a pirated movie than to make an ISO. – Gantendo Nov 27 '23 at 18:49
  • ... Or simply use a tool like Handbrake to make a much smaller file. – ChanganAuto Nov 27 '23 at 19:16
  • ok, yes, I don't know if the dvd is copy protected or not, perhaps it is. I thought that dd would be capable of handling such thing (I don't know how copy protection really works). – Eduardo Nov 27 '23 at 19:26
  • It does not, it merely images the drive and many copy protection technologies are based on thwarting what dd can do normally: https://en.wikipedia.org/wiki/Compact_Disc_and_DVD_copy_protection . Players work when and if they support DRM or otherwise rely on "codecs" that account for the other methods. Usually this is installed system-wide so tools like Handbrake work as well, but not dd. Again, if the purpose of imaging is to store a copy it's preferable to make it a much smaller MKV with the X265 (HEVC) codec. And I fail to understand why someone is using DVDs in this day and age but... – ChanganAuto Nov 27 '23 at 21:09
  • @ChanganAuto I prefer dvd/bluray etc as I want a physical copy, just as many others do. – Bib Nov 28 '23 at 10:51
  • @ChanganAuto you convinced me, I will use handbrake, even if I was looking for a more low-level solution, but it seems that I haven't acquired yet the knowledge to do so. Thank you for the hyperlink to wikipedia. At the library, that is the support they use to share certain documents such as films and documentaries. I will accept you answer if you answer it. – Eduardo Nov 28 '23 at 11:12

0 Answers0