Create .dmg from USB and restore it

Discussion in 'Apple Desktop Hardware/Software' started by daehenoc, Jun 18, 2019.

  1. daehenoc

    daehenoc Member

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    Hi all,

    I created a USB installer for el Capitan, and confirmed that it boots and successfully installs el Cap. Hooray me. I want to create a dmg (or ISO) file of that USB, then restore that to another USB.

    I created the installer on el Cap, then followed these instructions on a laptop with Mojave to create a dmg file:
    https://support.apple.com/en-au/guide/disk-utility/dskutl11888/18.0/mac/10.14

    How do I then successfully restore that dmg file to another USB? Every time I've tried, I wind up with only the 'Packages' folder in the root of the target USB and that doesn't boot a mac to install el Cap!

    Am I doing it wrong, should I try creating an ISO or something else entirely?

    Thanks!

    Edit: The reason I ask this is so that I can have a .dmg (or ISO) file of older versions of macOS, that I can restore to a USB key from any version of macOS. (e.g. the createinstallmedia executable from the el Cap installer doesn't work from Mojave...)
     
    Last edited: Jun 18, 2019
  2. [KEi]SoVeReIgN

    [KEi]SoVeReIgN Member

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  3. OP
    OP
    daehenoc

    daehenoc Member

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    Really, I should restate the problem:

    I am creating a macOS 10.11 boot USB using createinstallmedia on an older MBP, all OK. I then want to take an image of that USB, so I can put it on other USBs or reuse that USB for some other purpose. I thought that using Disk Manager to make a .dmg of that USB would be hunky dory, but when I follow the Apple instructions for restoring that .dmg to a USB (even the same USB I took the image from!), I can't boot off that USB.

    When I restore the .dmg to the USB, all I can see on that USB is the Packages folder, the "Install OS X el Capitan" icon isn't in the root of the drive, and it won't boot.

    Should using Disk Manager to take an image to a .dmg and restore it work? Am I doing it wrong? Help!
     
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    daehenoc

    daehenoc Member

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  5. fad

    fad Member

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    I had to do this, I downloaded the install dmg from the app store and used a program to make the usb.
     
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    daehenoc

    daehenoc Member

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    Solved! When creating a .dmg file from the install USB, I was selecting the partition, not the physical media! duur.

    I'm going to write this up as a guide, to help others figure this out. Will post.
     
  7. flu!d

    flu!d Ubuntu Mate 16.04 LTS

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    You can do it under terminal, no need for some stupid app.
     
  8. elvis

    elvis Old school old fool

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    dd. Two letters and 54KB of spectacular goodness.
     
    flu!d likes this.

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