Boot camp off external hard drive

Roadking714

macrumors regular
Original poster
Mar 7, 2014
182
1
Can I run Windows in boot camp off a external hard drive to save space on my rmbp if so any links on how to? Thanks in advance
 

austinpike

macrumors 6502
Oct 5, 2008
313
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MN
You can run windows off an external thunderbolt drive, but I don't think it will work with USB. I use an SSD on one of these Seagate TB sleds to boot my Mac Pro into windows 8. The windows installer just sees the TB drive as another SATA bus so I don't think I even had to do anything special. Skip the boot camp assistant altogether, make a USB drive installer for whatever windows flavor you are using and you should be able to format and install directly to the external drive.

There may have been some trickery to get the boot camp drivers installed after the fact, sorry I don't recall the exact steps.
 

Freyqq

macrumors 601
Dec 13, 2004
4,014
166
Consider Microsoft remote desktop as an option too, if you have an extra PC lying around.
 

yjchua95

macrumors 604
Apr 23, 2011
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GVA, KUL, MEL (current), ZQN
Can I run Windows in boot camp off a external hard drive to save space on my rmbp if so any links on how to? Thanks in advance
Steps:

Connect external drive to Windows VM. You must have a Windows VM in VMware/Parallels/VBox, or a Windows PC. Any existing Windows environment will do.

What you need:
install.wim file (obtain this from your Windows ISO)

Open elevated cmd.exe (run as admin)

Note: All commands aren't case sensitive, including pathway to files.

Type diskpart
Type list disk
Take note of the disk you want to select
Type select disk 1 (if your disk is Disk 1)
Type clean
Type convert gpt (stop at this point if you're using a Thunderbolt drive)
Type create partition EFI size=100 (skip if installing in BIOS-CSM)
Type format quick fs=fat32 label=EFI (skip if installing in BIOS-CSM)
Type assign letter=S (skip if installing in BIOS-CSM)
Type create partition primary
Type format fs=ntfs quick label=W2G (or any other name you wish for label)
Type assign letter=E
Type exit

Open up File Explorer. In your C drive, create a new folder named WIN2GO.
Put the install.wim file in this folder

Back in cmd.exe:
Type dism /apply-image /imagefile:C:\WIN2GO\install.wim /index:1 /applydir:E:\ (this process will take quite a while)
Type E:\Windows\System32\bcdboot E:\Windows /s S: /f UEFI - use this one for UEFI installation
Type E:\Windows\System32\bcdboot E:\Windows /s S: /f ALL - use this one for BIOS-CSM installation

Restart your entire Mac. After the chime, hold down Option and when prompted to select your boot drive, select EFI Boot.

Proceed installation normally.

After installation, install Boot Camp drivers. Feel free to trash the VM once you're done too.

For best results, use USB 3/Thunderbolt. If you don't have USB 3, use Thunderbolt. If you have neither, stick back to the internal drive :)

Note: This method involves reformatting the entire external drive.

For Thunderbolt drives, just boot from the Windows USB installer and install directly onto the TB drive. Windows sees TB drives as an internal PCIe connection. However, you must format the TB drive as GPT first.

CAUTION: Windows can only be installed in UEFI flawlessly on Haswell Macs and later. Ivy Bridge and earlier Macs can only run Windows in BIOS-CSM flawlessly. Attempts to boot a UEFI installation of Windows on an Ivy Bridge or earlier Mac will result in driver issues.



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You can run windows off an external thunderbolt drive, but I don't think it will work with USB. I use an SSD on one of these Seagate TB sleds to boot my Mac Pro into windows 8. The windows installer just sees the TB drive as another SATA bus so I don't think I even had to do anything special. Skip the boot camp assistant altogether, make a USB drive installer for whatever windows flavor you are using and you should be able to format and install directly to the external drive.

There may have been some trickery to get the boot camp drivers installed after the fact, sorry I don't recall the exact steps.
See my steps above. It's possible over USB.
 
Last edited:

panzer06

macrumors 68040
Sep 23, 2006
3,009
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Kilrath
Can I run Windows in boot camp off a external hard drive to save space on my rmbp if so any links on how to? Thanks in advance
I just cloned my existing Windows PC running EFI Windows 8 and put the clone in a TB enclosure. Once it booted I installed the bootcamp drivers. Because my 2011 iMac doesn't fully support EFI I got no sound. Had to buy a USB sound card. Just plugged it in and it worked on OS X and Windows automatically.

With the EFI issue I do have to hold the ALT/Option key to manually select EFI Boot. Selecting Boot to Windows in Systems Prefs gets a No boot device error. Other than that it works well. And yes, it will boot off USB as well. Not sure Windows 7 will do that. USB is too slow tho. I have SSD in my enclosure so it's very fast.

Cheers,
 

UniDoubleU

macrumors regular
Aug 14, 2014
160
1
Thailand
I'm running an SSD off external USB3 drive with Windows 8.1 on it. Winclone never seem to work fine, some drivers problem. Though I haven't tried it, I'm sure TB drive should work fine with Winclone. So I made a clean install with WinToUSB in VMware (any solution is fine as long as you can boot to Windows). Make sure to have the driver partitioned with yjchua95's method first also, no need to find any .wim file.
 

yjchua95

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Apr 23, 2011
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I'm running an SSD off external USB3 drive with Windows 8.1 on it. Winclone never seem to work fine, some drivers problem. Though I haven't tried it, I'm sure TB drive should work fine with Winclone. So I made a clean install with WinToUSB in VMware (any solution is fine as long as you can boot to Windows). Make sure to have the driver partitioned with yjchua95's method first also, no need to find any .wim file.
Can WinToUSB install Windows 8.1 in a UEFI environment?
 

UniDoubleU

macrumors regular
Aug 14, 2014
160
1
Thailand
From what I've heard, some people have trouble getting drives made by WinToUSB to boot.

Can it boot into BIOS-CSM environments as well?
I'm not so sure about that. From my experience you need an EFI partition during the setup/install process. Try it out? It's free!
 

yjchua95

macrumors 604
Apr 23, 2011
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I'm not so sure about that. From my experience you need an EFI partition during the setup/install process. Try it out? It's free!
Sadly, I don't have an empty external drive that I'm willing to erase for testing :p

Each to his own, I guess, but I'm more comfortable in executing stuff in which I clearly know what commands are executed. WinToUSB automates everything and I'm not comfortable with it, because I can't fully see the commands that are executed.
 

UniDoubleU

macrumors regular
Aug 14, 2014
160
1
Thailand
Sadly, I don't have an empty external drive that I'm willing to erase for testing :p

Each to his own, I guess, but I'm more comfortable in executing stuff in which I clearly know what commands are executed. WinToUSB automates everything and I'm not comfortable with it, because I can't fully see the commands that are executed.
Well, seeing as you're already preparing to create one anyways I assume you've got one to setup. If it doesn't work then reformat and try another method. Took me a week before clean install with WinToUSB lol. :eek:
 

TPadden

macrumors 6502a
Oct 28, 2010
628
218
Well, seeing as you're already preparing to create one anyways I assume you've got one to setup. If it doesn't work then reformat and try another method. Took me a week before clean install with WinToUSB lol. :eek:
Took me less than 10 hassle free minutes to get Windows 10 running on external Samsung 840 EVO SSD, Inatek Sata 3, UASP, USB3, enclosure, with WintoUSB. The only hard part was getting the Win 10 ISO, which I already had. It can be converted from an ESD file.

To get the ESD after initiating the Win 10 download, and as soon as the install starts, go to C:\$Windows.~BT\Sources and copy install.esd to another location. You should also find the ESD file after updating to the new build in C:\RecoveryImage.

•Download the ESD Decrypter tool

http://www.chris123nt.com/ESDTool/esd-decrypter-v4c.7z

Once you have your desired ESD and the tool, extract the tool anywhere you see fit (ex: C:\ESDTool) and place the ESD file in the same folder.

Run the cmd file and you will be presented with a list of options. Option 4 will give you the traditional ISO with a boot.wim and install.wim. This is the option you want to make a traditional Windows ISO.

Let the tool run, and when it is done you will have a fully functional Windows 10 build 9860, 9926 or whatever your build ISO that you can use to perform clean installs as you see fit. And you will have no problems getting future build updates if you use this method as well.


Used my Windows desktop to install it using WintoUSB, plugged into MBA, option booted, and installed Bootcamp drivers, it ran immediately (fast).

For some reason others haven't been so lucky.
 
Last edited:

UniDoubleU

macrumors regular
Aug 14, 2014
160
1
Thailand
Took me less than 10 hassle free minutes to get Windows 10 running on external Samsung 840 EVO SSD, Inatek Sata 3, UASP, USB3, enclosure, with WintoUSB. The only hard part was getting the Win 10 ISO, which I already had. It can be converted from an ESD file.

To get the ESD after initiating the Win 10 download, and as soon as the install starts, go to C:\$Windows.~BT\Sources and copy install.esd to another location. You should also find the ESD file after updating to the new build in C:\RecoveryImage.

•Download the ESD Decrypter tool

http://www.chris123nt.com/ESDTool/esd-decrypter-v4c.7z

Once you have your desired ESD and the tool, extract the tool anywhere you see fit (ex: C:\ESDTool) and place the ESD file in the same folder.

Run the cmd file and you will be presented with a list of options. Option 4 will give you the traditional ISO with a boot.wim and install.wim. This is the option you want to make a traditional Windows ISO.

Let the tool run, and when it is done you will have a fully functional Windows 10 build 9860, 9926 or whatever your build ISO that you can use to perform clean installs as you see fit. And you will have no problems getting future build updates if you use this method as well.


Used my Windows desktop to install it using WintoUSB, plugged into MBA, option booted, and installed Bootcamp drivers, it ran immediately (fast).

For some reason others haven't been so lucky.
There you go! The week I mentioned was spending most of my free time after work trying to migrate my previous Bootcamp partition to work. Better to just do a clean install then copy whatever you need over. Your NTFS Bootcamp partition should be readable by the external installation.