man tar says that OS X's tar implementation should be able to extract .iso files.

tar creates and manipulates streaming archive files. This implementation can extract from tar, pax, cpio, zip, jar, ar, and ISO 9660 cdrom images and can create tar, pax, cpio, ar, and shar archives.

However, tar gives me the following error:

$ tar -xvf test.iso
tar: Unrecognized archive format
tar: Error exit delayed from previous errors.

What's with the discrepancy?

The .iso is created from a .dmg using Apple's hdiutil utility. poweriso can extract it without issue.

I'm on OS X 10.7.4. tar --version reports bsdtar 2.8.3 - libarchive 2.8.3.

1 Answer 1


Chances are that it is not a pure ISO image so tar may not recognize it. I have tested tar on some random ISO images and it could handle them all, so it's likely specific to that particular image. Note that hdiutil can create non-ISO CDR images so you would have to explicitly tell it to use the ISO format (note that the ISO format is somewhat restrictive, so many CDs use a different format either in addition to ISO or instead of it).

  • 1
    I used hdiutil convert -format UDTO -o foo foo.dmg. I don't see any way to be more specific with the desired output format. I will try to find some more .iso files to test.
    – Maxpm
    Dec 20, 2012 at 4:36
  • I tested it with a couple more files, and it silently failed for them. There were no error messages, but it didn't extract anything. Are you sure you're using the same version of tar and OS X as I?
    – Maxpm
    Dec 20, 2012 at 19:45

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .