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[Solved] Prohibitory sign when booting from install USB

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Motherboard
Gigabyte GA-Z77-D3H
CPU
Intel Core i5-3570K OC'd to 4.08 GHz
Graphics
MSI R7870-2GD5T/OC (2GB)
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[RESOLVED] Prohibitory sign when booting from install USB

Hi everyone,

I have a fully functioning Mavericks installation running right now. My build is such that I don't even need to run Multibeast when I do a fresh install - I just need to use the iBoot USB to boot, and I use an external USB sound card. In other words, up till now, I've had no hardware that causes any big issues with OS X.

I followed Tony's guide to upgrade to Yosemite directly from Mavericks here: http://www.tonymacx86.com/yosemite-...-os-x-yosemite-using-unibeast-multibeast.html, creating an install USB. However, when I try to boot into the installer from my new USB, after a few minutes of loading (maybe at about 30%) the screen goes fully gray and I get a prohibitory sign. The installation halts completely.

Since all of my hardware has seemed very OS X-friendly so far, I can't begin to imagine what the problem is. You can see the details of my build on my profile, but I'm pasting here as well:

Motherboard
Gigabyte GA-Z77-D3H

CPU
Intel Core i5-3570K OC'd to 4.08 GHz

Graphics
MSI R7870-2GD5T/OC (2GB)

Other Hardware
2x4GB G.SKILL Ripjaws X @ 1600 MHz
2x2GB Micron @ 1333 MHz
Sound Blaster X-Fi Fatal1ty
250GB Samsung 840 (Win8)
250GB WD @ 7200 (Win7)
160GB WD @ 7200 (Mavericks)
500GB Seagate @ 7200 (Storage)

I'd appreciate any help you guys can give me. Please tell me if any other information would be helpful.

Thanks.

UPDATE: So I'm currently posting this from inside Yosemite! MASSIVE ups to Fjordn for asking me to make sure I was using a USB 2.0 port instead of a USB 3.0 port. I moved the OS X Installer USB to a USB 2.0 port on the back of my motherboard, instead of my USB 3.0 ports on the front of my case, and on the first try everything worked as smooth as butter. Not a single boot flag or hardware change. So folks, when you're installing, DON'T TRY TO USE A USB 3.0 PORT.
 
Last edited:
Yosemite is the first major upgrade that caused me trouble too. I recommend you to try a clean install
 
try to boot with -x -v -f option. it works for me.
 
Sorry, I think I made my first post too ambiguous. My problem is not that I can't boot into my Yosemite installation - it's that I can't INSTALL Yosemite because the loader on the install USB gives me the prohibitory sign before it completes.

Yosemite is the first major upgrade that caused me trouble too. I recommend you to try a clean install

I'm not completely against it, but when it's just loading files for installation, shouldn't it not matter what I already have on my hard drive? I mean, what if I were to try and do a clean install? I simply can't load the installer at all.

try to boot with -x -v -f option. it works for me.

You mean boot the installer itself in safe-mode? I didn't know that was possible, but I'd be very happy to try.
 
I'm tying to remember what i did exactly since i did the upgrade a couple of days a go and I ran into so many problems.

I believe I always boot using the motherboard boot option to avoid that "mach_kernel" error. After the upgrade was successful I still have to boot from the usb one more time using the boot option.

After the boot option display I chose the bootable usb then i choose to boot from my SSD with the option -x -v -f. I actually have to disconnect all of my monitors from the graphic card and only connected one monitor directly to the motherboard.

I hope this help :)
 
What do you mean by "motherboard boot option"? Do you mean just specifically telling the computer to boot off the USB, or is that some sort of boot flag?

Also, what you said about the graphics reminded me of something. I now remember that having an AMD 7000 series card causes some problems with boot, so maybe it's best to swap in my VGA monitor directly connected to the motherboard just for install...

I'm just wondering, though, has anyone else specifically experienced the prohibitory sign ("No" symbol, if you prefer) during a Yosemite upgrade? Was anyone able to resolve theirs?
 
Oh... oh damn! That could totally be it! I'm using the front-side USB 3.0 ports on my case! I've been using those to boot my Mavericks install just fine, but that could totally be causing this problem.

I'll try a different USB port, then try swapping out the monitor and see if one of them works.

Does anyone have any other possible fixes?
 
By motherboard boot option I mean "boot option" during start up. Sorry for the confusion.

you are using gigabyte board same as me, so just hit f12 during boot up.
 
Oh, okay, that's what I've been doing every time as well. Thanks for clarifying!
 
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