Yosemite hangs on USBMSC identifier

[brephil]

I was struggling with Yosemite, when restarting the boot hung on USBMSC identifier. I found some information that Yosemite does not load "unsigned" kexts. The fix for me was to add the following to my org.chameleon.Boot.plist:
<key>Kernel Flags</key>
<string>kext-dev-mode=1</string>


This seemed to force the loading of the kexts and all is well. This may be old info, but I could not find anything. Hoping this helps someone

 

[vkfresh]

I have a similar issue but the kext dev isnt fixing it for me

 

[beelzebozo]

MultiBeast for Yosemite already has that kernel flag available to add.

 

[brephil]

Hmm... that is exactly where mine hung too... I tired all the tricks I could think of, but the only way it would start was in safe mode.
1. Removed all USB devices other than my keyboard
2. Tired the following flags (one at a time) : USBBusFix=Yes, USBLegacyOff=Yes, config=Null, and smibios=Null

When I hit F8 on a restart using my USB thumb drive it booted fine in "normal" mode.

This is when I noticed some differences in the org.chameleon.Boot.plist between USB and Mavericks Volumes. I re ran my MulitBeastv7 config (from the USB volume, not sure I did that the first time, not sure it maters either) and added that flag in the boot options, and this got me going. Not sure what else changed.

Here is the value of that flag right now on my Mavericks volume:
<key>Kernel Flags</key>
<string>kext-dev-mode=1 nvda_drv=1</string>

 

[beelzebozo]

It helps when asking for help to include your hardware specs. Nobody can tell what you have unless you specify.

 

[psychosync]

I found a way around that. It seems that Yosemite has a kext signing feature that prevents booting if we install whatever modified kext. At first i was always booting with -f flag and it worked but i wanted something permanent and not just editing chameleon plist file. Try this:

If you can boot in safe mode or any other way:

In terminal type:
sudo -s
touch /Volumes/<YOUR DISK>/System/Library/Extensions
kextcache -u /Volumes/<YOUR DISK>

If you simply cannot boot your OS, maybe try these commands from terminal with your installation usb key or DVD.

 

[cidus]

Hello everyone

I'm having the exact same issue, boot from HDD hangs at USBMSC identifier.
I have tried every step cited above and nothing helps.
I had a working Mavericks, installed Yosemite over it, and cannot boot ever since.

The installation boots fine, but I cannot boot into HDD after install, not even when booting from USB first, and not with any boot flags (-x -f -v), I have used UniBeast 5.1.0

I have read that removing IOUSB kexts would boot without USB support, but that does not work also. Boot hangs in a previous step. I don't believe it has anything to do with USB.

My MB is Intel DP55WB, Graphics Radeon HDX850, processor i5 750.

 

[cidus]

This is my boot screen:

 

[msm]

I found a way around that. It seems that Yosemite has a kext signing feature that prevents booting if we install whatever modified kext. At first i was always booting with -f flag and it worked but i wanted something permanent and not just editing chameleon plist file. Try this:

If you can boot in safe mode or any other way:

In terminal type:
sudo -s
touch /Volumes/<YOUR DISK>/System/Library/Extensions
kextcache -u /Volumes/<YOUR DISK>

If you simply cannot boot your OS, maybe try these commands from terminal with your installation usb key or DVD.

This worked for me after a fresh install of Yosemite. I tried every solution I read about, but this is the one that finally worked.

Thanks!