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I'm working on upgrading a system from RHEL6 to RHEL7 and in the meantime I need to do a few tests before I actually upgrade. My question is: I have a working RHEL7 stock ISO file downloaded from Red Hat's website, and I attempted to copy the contents of the ISO to a folder on my computer, and then turn that folder into a new ISO (using various ISO-creating utilities), just to make sure I could do that. However, the problem is, despite me making no changes before "recompiling it", when I try to use this recreated ISO in VirtualBox, I get a fatal error: no bootable medium found error. What could be causing this?

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  • Is the file structure the same in your new ISO? For example, the new ISO might have the OS stuff in yourfolder->OS inside of the ISO.
    – imtheman
    Jun 22, 2016 at 21:11
  • If the files structure is the same then you need to make sure you are creating a bootable ISO. intowindows.com/how-to-add-files-to-bootable-iso-in-windows
    – imtheman
    Jun 22, 2016 at 21:19
  • 3
    Possible duplicate of Create bootable RedHat iso from folder
    – imtheman
    Jun 22, 2016 at 21:22
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    To be bootable a disk has to have a valid boot sector. When you copy the contents, (...), and you make a new disk without the correct boot sector you have a normal disk full with the data. Check here about how to do a bootable iso image. (Look for -b option of genisoimage). Minimal guide.
    – Hastur
    Jun 22, 2016 at 23:09
  • ps> Welcome on SuperUser.
    – Hastur
    Jun 22, 2016 at 23:13

2 Answers 2

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Steps for copying and doing a fixup on an iso image:

  1. Make a temporary directory for the contents of your iso:

    # mkdir /var/tmp/isodir
    
  2. Make a temporary mount dir for the iso:

    # mkdir /id
    
  3. Mount the iso:

    # mount -oro,loop /path/to/file.iso /id
    
  4. Copy the contents to the new path:

    # cd /id
    # cp -av . /var/tmp/isodir
    
  5. Go over into /var/tmp/isodir and do whatever mods you need.
  6. Recreate your .iso:

    # cd /var/tmp/isodir
    # mkisofs -o /path/to/new/file.iso -b isolinux.bin -c boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -R -J -v -T isolinux/
    
  7. Cleanup:

    # umount /id
    # rmdir /id
    

Explanation: The mkisofs command above uses the -b flag to specify the boot image (isolinux.bin). (The rest of the flags can be found in the man page for mkisofs.)

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  • Thanks a lot! I've gotten the rebuilt ISO to boot, although it's getting stuck in the install process.
    – cmoughon
    Jun 23, 2016 at 15:16
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To be bootable a disk has to have a valid boot sector. When you copy the contents, (...), and you make a new disk without the correct boot sector you have a normal disk full with the data. Check here about how to do a bootable iso image. (Look for -b option of genisoimage).

Look here for a Minimal guide.

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