How to make a bootable Thumbdrive of OS X

osx installer

It’s very handy to have a bootable version of OS X on a thumb drive.

I have written how to do this using a program called DiskMaker X,  and I have written about how to do it from the command line here,  but after doing this a few times I find the most reliable method is the one outlined below.   It uses Apple’s built-in disk utility.This works with any version of OS X. Mountain Lion, Yosemite, El Capitan etc. You’ll need an 8G USB thumbdrive.

1. Purchase or download the OS X Installer via the App store. It will look something like this:


2. Right-click on the installer and select “Show Package Contents. ”  Open the ‘SharedSupport’  folder and find  the file called  â€œInstallESD.dmg”.

3. Insert the thumb drive and use disk utility to format it as Mac OS Extended (Journaled) with GUID Partition Table.

4. Use Disk Utility to ‘Restore’ the dmg file to a thumb drive. Select the thumndrive in disk utility and then go to the ‘Edit’ Menu of Disk Utility and select ‘Restore.’ It will prompt you for a disk image. Select the ‘InstallESD.img’ file.

This will make an OS X Installation USB drive like you buy from the Apple Store.



2 responses to “How to make a bootable Thumbdrive of OS X”

  1. matthias

    Hi does the disc utility method work with installing el capitan on a snow leopard mac? are there specific instructions what to do after making the bootable drive then attaching it to other computer? I tried it and the smaller packages load onto the hard drive but the mpkg doesnt recognise the native drive,

  2. Blota

    Switch out the cable use apple product cable and check the color code online use the correct 2.0, 3.0, 3.1 ….etc. Try restarting the mac after its up to date. Try a different usb port-clean contacts if you must.
    ?The USB port is not working properly.

    ?Virus attack or insufficient power supply of the USB ports.

    ?There are bad sectors on the flash drive.

    ?USB driver is not installed properly.

    ?USB driver is out of date.

    ?File system is corrupted.

    ?USB device is disabled in BIOS.

    if that doesn’t work consider purchasing, latest products. Here are a couple I highly recommend.

    SanDisk 128GB Extreme PRO USB 3.2 Solid State Flash Drive read to 420MB/s; write speeds 380MB/s $50
    SanDisk 64GB Extreme Go USB 3.2 Read Speed 400 Megabytes Per Second $20


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