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Reasons for wanting create such a usb include:

  • PC is unbootable and you want to prepare a bootable USB using the ISO file that you have on your external hard drive.
  • to install Windows 8.1 on Mac without Boot Camp.

What are the necessary steps to create such a Windows 8.1 bootable usb on a Mac ?

Simon
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3 Answers3

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I am not really sure why you would want to install Windows 8.1 without BootCamp.

The USB stick needs to be a little bigger than the .iso file you are going to be burning. It doesn't matter if there is any data on it, this will totally erase the whole thing.

Steps To Achieve Victory

  1. Download the ISO you want to use

  2. Open Terminal (in /Applications/Utilities)

    2.1 Navigate to the path where the .iso file is located

    2.2 Use ls to list all the folders

    2.3 cd /path/to/iso to dive in to folder or cd .. to go back the path

  3. Convert .iso to .img using hdiutil:
    hdiutil convert -format UDRW -o /path/to/target.img /path/to/source.iso
  4. Rename if OS X gave it a .dmg ending:
    mv /path/to/target.img.dmg path/to/target.img
  5. Type diskutil list to get a list of currently connected devices
  6. Insert USB drive you want to use
  7. Run diskutil list again to see what your USB stick gets assigned eg - /dev/disk3
  8. Run diskutil unmountDisk /dev/diskN (where N is the number assigned to your USB stick, in previous example it would be 3)
  9. Run sudo dd if=/path/to/target.img of=/dev/diskN bs=1m (if you get an error, replace bs=1m with bs=1M
  10. Run diskutil eject /dev/diskN and remove your USB stick
  11. The USB stick will now be ready to use

IMPORTANT For the step #9 you can use the destination to /dev/rdiskN to reduce the copy time.

NOTE: Sometimes, not always, Step #4 will be necessary. Not all the time. I am not sure why it will add the .dmg ending and other times leave it alone.

NOTE 2: Might I suggest you learn the name of the .iso you downloaded, or just rename it win8.1.iso or something, and put it on your Desktop folder. That way, when you are typing commands like #3 and #4 etc, etc, you can type it like this:

hdiutil convert -format UDRW -o ~/Desktop/win8.1.img ~/Desktop/win8.1.iso

and 

mv ~/Desktop/win8.1.img.dmg ~/Desktop/win8.1.img

and step #9 would look like this:

sudo dd if=~/Desktop/win8.1.img of=/dev/diskN bs=1m

IMPORTANT - You can track the progress by pressing CTRL + T It will show the process info and records in and out, since we use the bs=1m each record is 1Mb in size so you can easily track the progress.

I don't mean to be insulting with Note and Note2, I am just making sure that you know what all these commands mean. It's the simplest method. Unless someone else comes up with something better.

JohannesM
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Danijel-James W
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  • No insult taken. Thankyou for being clear & concise in your answer. – Simon Oct 01 '13 at 10:41
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    I also had a look over here, http://apple.stackexchange.com/a/62700/49601 they have a solution that might be a little easier to work with if you need it. I'm a Terminal freak, so I try to do as much as I can with this utility instead of apps. – Danijel-James W Oct 01 '13 at 11:24
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    Out of interest is using terminal detrimental in anyway to OSX ? – Simon Oct 01 '13 at 11:30
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    Terminal is amazing. Terminal is the underlying system in OS X. Well, kind of. OS X is actually a form of UNIX called BSD. Terminal is the "console" if you will, the way you can interact with it. It's not detrimental to OS X, and it works way better because it gives you direct access to functions otherwise hidden from you. I hated it at first, it's like Command Prompt on Windows, but then I got the hang of it over the years and now can't live without it. – Danijel-James W Oct 01 '13 at 11:36
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    It is easy to spot, when ever it asks you for your password to be able to execute your request, be careful. – Ruskes Oct 01 '13 at 11:38
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    @DanijelJames I think your solution is better than the link you have shown in the comment above. May I ask where can I learn how to do Terminal "hacks" for OS X ? – Simon Oct 01 '13 at 11:39
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    Also read this before fooling arround :) http://forums.macrumors.com/showthread.php?t=738396 other than that enjoy. – Ruskes Oct 01 '13 at 11:44
  • @Buscar웃 said it well. It can be detrimental when it asks you to enter a password. So be mindful of what you are typing from a well-versed source.

    Simon, the best place to learn Terminal for OS X is to start on here. It's about finding what you want to do before you learn how it works. Bash Scripting is the goldmine that will open your mind to what the Terminal can be used to do. There are other scripting languages like Korn and C-shell, but I don't use them. Otherwise just troll websites and Google. Or, know what you want to do, and ask here!

     – Danijel-James W Oct 01 '13 at 11:44
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    @DanijelJames Thanks for the advice. I might also checkout to see if there is any suitable publication, ebook or otherwise around the subject area. – Simon Oct 01 '13 at 11:47
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    @Buscar웃 Thanks also for your advice & appropriate link. – Simon Oct 01 '13 at 11:48
  • I am still learning the basics of it, but there are some safe one to play with it: like "Airport" to show you your networks, or the IFconfig, or the Netstat, and many others, which are harmless and just show you specific information. You can play with those commands first. – Ruskes Oct 01 '13 at 11:51
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    @Buscar웃 I think it can also be said: Always remember to use Terminal ONLY when you are confident in what you are doing, since a simple mistake when using this utility can cause some serious damage to your Mac. – Simon Oct 08 '13 at 11:52
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    I find that whenever I am supposed to write some path for a file in Terminal I just drag and drop the file I am changing from what ever folder it is placed in into the Terminal window after the command, so in step 3 I would write: hdiutil convert -format UDRW -o Remember the line should end with a space. Then drag the ISO file into Terminal, change the ending from ISO to IMG and drag the ISO file into Terminal again ... et voilà ... two perfect paths without having to guess at it. Hope this helps ;) – FlashGirl Nov 15 '13 at 02:36
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    I followed these steps and ended up with a USB stick that showed as non-bootable. Does anyone have any idea what could have gone wrong? (As for why you'd install Windows 8.1 without Boot Camp: because you're preparing the USB stick on a Mac in order to install Windows on an Intel NUC :) – John Y Mar 16 '14 at 14:27
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    If the ISO isn't a bootable ISO to begin with, and just a raw data dump,then it is missing the sectors that need to be written using dd to the USB. Which version of 8.1 are you using, and where did you get it from, or how did you get it? I might be able to help you. – Danijel-James W Mar 18 '14 at 13:34
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    While this worked... I must say that I almost gave up. Step 9 took many hours (guide should note this):

    3708465152 bytes transferred in 29540.931255 secs (125537 bytes/sec)

     – Thomas Jespersen Mar 19 '14 at 09:30
  • @ThomasJespersen, there might be something wrong with your USB stick as it shouldn't be that slow. It took about 6 minutes on my 5 years old laptop. – laurent Mar 24 '14 at 02:24
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    Might be... still guide should notice this as there is no progress indicator. I ended up creating the bootable USB key using Windows which took 23 min. (same USB key). – Thomas Jespersen Mar 24 '14 at 07:46
  • @ThomasJespersenI added an extra note regarding the progress bar, maybe your USB stick is old? – Danijel-James W Mar 28 '14 at 12:23
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    This does not work. These are the same instructions that Ubuntu posts on their site for making a live USB and there have been several questions on superuser about this process not working. – 2rs2ts Jul 11 '14 at 17:56
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    I tried to use this for Win 7 install - but USB stick was not recognized by PC. (all files showed up when I viewed w/ my mac) My guess is that I needed to reformat to something other than Fat32 first? I ended up using a windows box to create the install stick. – evilblender Sep 09 '14 at 19:47
  • didn't work for me. – Meekohi Oct 10 '14 at 03:28
  • USB stick shows as bootable, but if selected, standard message appears "invalid boot disk, select proper boot sisk, blah blah blah". – Display Name Nov 23 '14 at 13:47
  • One reason one might need to do this without BootCamp Assistant is if they're using a hackintosh. So thank you. Cheers! – Armel Larcier Jan 15 '15 at 17:59
  • Yeah, it took multiple hours for me as well, and I have a 6 year old macbook. – McKay May 24 '15 at 19:17
  • And when it was finished. It wasn't recognized by my windows computer as even a formatted disk., – McKay May 24 '15 at 19:37
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    Per the OP: You would want to install Windows 8.1 without Bootcamp for models like the Mid 2009 MacBook Pro that are not supported by Bootcamp, but can still dual-boot Windows 8.1. – Rampant Jun 10 '15 at 02:26
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    To make it bootable, in some cases (when disk is partitioned with Apple partition scheme, this is visible in diskutil list output) you'll need to re-partition the whole disk, as described here: http://www.techrepublic.com/blog/user-support/the-right-way-to-format-windows-disks-using-a-mac/. After repartitioning, repeat the steps above again. – skozin Sep 27 '15 at 23:01
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    awesome tut. always impressive how some people master the terminal... i was able to create a working win7 boot stick with macOS sierra. for my mum's crappy old windows laptop... without this i would have been screwed... – David Seek Nov 20 '16 at 00:06
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    can you please explain why rdisk make it run faster? – genuinefafa Jun 12 '18 at 23:32
  • @genuinefafa see this post https://superuser.com/a/631601/256923 – Danijel-James W Jun 13 '18 at 21:24
  • I think some older boxes can't boot of GUID, only MBR. So I had to go to a windows box and use Rufus, then it worked...or boot camp – rogerdpack Jan 15 '19 at 14:33
  • Does not work. I burned a Windows 7 Flash USB as by this answer. MacOS can see it as an UDF volume (bootable via macos' qemu), but other Windows 7 machines see it as unformatted RAW and it is not bootable in fact. – Pavel Vlasov May 20 '19 at 08:56
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I would have liked to comment on the previous answer, because it's a (nearly) perfect description of what to do (at least for the Linux distros I've been working through over the past week), but I'm shy of the 50 rep needed for comments…

Anyway, to supplement @danijel-j's answer, I discovered that (some?) of the USB keys I was using required me to partition them before the BIOS on the netbook I was working with would recognize them (presumably they had no MBR/GPT for the machine to read). I did the partitioning with Disk Utility.app, but I'm sure working through it with diskutil would be just as easy (I still don't know the CLI commands and options for diskutil).

Dustin Wheeler
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  • Hi there, Thanks for pointing this out. I'll supplement my answer using Disk Utility and Terminal later today to show everyone what you are talking about. – Danijel-James W Mar 06 '16 at 00:58
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This is terrible, but abandon all efforts to create this from OSX Mojave 10.14.4. I tried all the methods, I am a proficient power user and nothing worked. While I was continuously able to create a bootable usb drive, it failed on the windows installation with A media driver your computer needs is missing.

I verified the downloaded iso, redownloaded etc, to no avail.

What did work:

Boot into parallels in a windows os, use the windows media creation tool and create the usb drive.

Booted, installed without issue.

TL;DR it is absolutely ridiculous that you cannot use osx native commands to make this work, but clearly Microsoft has failed to make this process easy from a mac. Use the windows media creation tool from any available windows os, including parallels will get you a bootable usb that will install without driver problems.

kross
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