HELP - Can't switch boot disk after installing Yosemite

Question

HELP - Can't switch boot disk after installing Yosemite

The start of my troubles can be found in this thread: Yosemite install strategy on multi-drive Mac Pro

(I'm starting this thread since the original title of that thread is now unimportant and it's unlikely anyone will respond to it - what's important is that I can't get back...)

Problem: After installing Yosemite, I can't change the startup disk.

I need to be able to switch the startup disk back to a different internal HD which has 10.6.8 Snow Leopard (and all my critical data and apps) on it.

Summary of how I got here:

I have an older Mac Pro (2009) with multiple internal hard drives (and multiple external drives). The primary internal drive (HD#1) is running 10.6.8. Snow Leopard. Internal HD#2 is (well, was) empty. I wanted to install Yosemite on HD#2, just to get it on the machine and try it out on this older (but still supported) platform. Most critical of all, I needed to preserve the existing data and apps on HD#1, as I plan to continue using Snow Leopard for most things. Having plenty of available drives, I figured this was a safe thing to try - switching boot drives is always easy. Right? Well, it was until Yosemite came along...
I downloaded Yosemite from the app store, and started installing. I chose to install it on HD#2, leaving my primary HD#1 untouched. It installed OK. Machine restarted, I was prompted to sign in, I did. As expected, it had booted off of HD#2 in Yosemite. I poked around for a while, satisfied that it was OK (if a bit slow). Time for me to switch back and boot off of HD#1 in good ole' 10.6.8 Snow Leopard and get some work done.
I open up System Preferences > Startup Disk. HD#2 with Yosemite is currently set as the boot drive, as I would expect. HD#1 (with 10.6.8) does appear there in the list of available drives, but all drives other than than HD#2 with Yosemite are greyed out. OK, I need to click the "lock" icon to make changes. I do. I get the authentication dialog. I'm prompted for username and password. I enter them. The credentials are rejected. WHAT??? I know the credentials are correct - I just used them as part of the installation. ???
I go to System Preferences > Users & Groups. Current User lists my name, but it shows as a "Standard" user account, NOT an admin. Hmmm. I click the lock icon to make changes to this account, I'm prompted for the "Admin" username and password. I enter my credentials. It rejects them, same as above. These are the same credentials I have always used for this machine under 10.6.8, and the same that I used when signing in to Yosemite at the conclusion of the installation. For some reason, it appears that Yosemite has decided to lock me out of this machine.
If I restart the machine, and hold down the Option key, the Startup Manager appears. It lists several drives. But my primary internal drive (HD#1) is not listed among them. Oh, great.

So I am at a loss as to what has happened here. I don't care about the (newly) installed Yosemite system on internal HD#2. I need to get this to point back to Snow Leopard on internal HD#1, which has critical data and work apps on it (and should be working fine). But for some reason, the default Yosemite installation has locked me out of simply switching startup drives (gee, thanks for that, Apple).

Help. How can I undo this mess? Thanks for any assistance.

Posted on May 25, 2015 4:22 PM

Reply

Answer 1

Best reply

den.thed

Level 9

77,176 points

May 25, 2015 6:02 PM in response to longtimemacuser666

Whatever you do from this point on, do not let Yosemite's Disk Utility or Spotlight anywhere near your Snow Leopard HD and Snow Leopard backups.

1. Try starting up from your Snow Leopard install disc and see if you can run Disk Utility Repair on HD#1.

2. If your Snow Leopard backup happens to be a clone, then you should be able to startup from it and use Disk Utility Repair on HD#1.

If you find that HD#1 has failed or is unreadable by Snow Leopard's Disk Utility. Then you may have to install Snow Leopard on a newly formatted HD using the Disk Utility on your Snow Leopard install disc and then restore it from your Snow Leopard backup.

Again, do not use the Disk Utility in Yosemite to format a new HD or anywhere near your Snow Leopard HD and Snow Leopard backups.

Reply

Answer 2

May 25, 2015 6:48 PM in response to den.thed

Well I dug out my Snow Leopard installation DVD and was able to start up off that. Thank heaven. I backed out of the initial Install screen, and there are menus to access. I chose Startup Disk. Thankfully, it does list ALL of the drives that have bootable systems, including my primary HD#1 that has the good Snow Leopard system on it. I chose that, and got it to boot back into good old Snow Leopard. Whew.

I'm inclined to just reformat that HD#2 (where Yosemite now resides) - the last thing I want is to inadvertently restart off of that sometime. Actually, I think I'll reformat that drive and use carbon copy cloner to replicate my primary (startup) Snow Leopard disk there, and keep Yosemite far, far away from this machine.

Time for a drink.

Reply

Answer 3

May 25, 2015 7:21 PM in response to longtimemacuser666

So now that Im back up and running on Snow Leopard, I'm noticing that the drive where Yosemite was installed is still doing a couple unexpected things...

1. I can't write to it. Any write operations require authentication. Sheesh.

2. I note that permissions for this HD are different from all the other disks attached to my Mac. On all the other HDs attached to this mac, the permissions are:

System: Read & Write

Admin: Read & Write

Everyone: Read Only

On the disk where Snow Leopard was installed, the permissions are:

System: Read & Write

Wheel: Read Only

Everyone: Read Only

Wheel !? I'm a little rusty on my unix permissions tweaks, but what the heck is this user "wheel"?

Is there no admin user on a Yosemite system?

(That might explain why it was rejecting my admin credentials when I tried to make any changes...)

I'm thinking I just need to format that hard drive, to banish all traces of Yosemite. Any reason I shouldn't do that?

Reply

Answer 4

Lanny

Level 6

13,183 points

May 25, 2015 7:30 PM in response to longtimemacuser666

This is a known issue. You can't use the Startup Disk System Precerence to switch to a 10.6.8 partition. There is nothing wrong with your partitions.

To switch to the 10.6.8 partition, restart your Mac while holding down the Option key to select the 10.6.8 partition. Use the same method to switch back to the Yosemite partition.

You should have searched the forums first. All of the things you have previously tried were wasted effort.

Reply

Answer 5

den.thed

Level 9

77,176 points

May 25, 2015 7:34 PM in response to longtimemacuser666

That is good news.

Your also going to find out that doing away with Yosemite is a real pain. Because you will first have to erase it while booted externally from Yosemite Recovery or from another copy of Yosemite's Disk Utilty on an External HD. Then use Snow Leopard's Disk Utility to reformat it before cloning or reinstalling 10.6.

Reply

Answer 6

May 25, 2015 8:02 PM in response to Lanny

Lanny wrote:

To switch to the 10.6.8 partition, restart your Mac while holding down the Option key to select the 10.6.8 partition. Use the same method to switch back to the Yosemite partition.

Nope. As I wrote above, holding down the Option key on booting does get to the startup manager, but the 10.6.8 disk does NOT appear there. So that was not an option. And I won't be switching back to the Yosemite disk (these are separate physical volumes, not partitions).

Reply

Answer 7

May 25, 2015 8:09 PM in response to den.thed

den.thed wrote:

That is good news.

Your also going to find out that doing away with Yosemite is a real pain. Because you will first have to erase it while booted externally from Yosemite Recovery or from another copy of Yosemite's Disk Utilty on an External HD. Then use Snow Leopard's Disk Utility to reformat it before cloning or reinstalling 10.6.

Hmmm. Can't I just reformat that disk (the one that got Yosemite installed on it)? I really don't care about anything on it - it was wiped clean before I installed Yosemite on it, and that's the only thing on it.

I'm now running comfortably again on Snow Leopard from my HD#1. Unless Yosemite did something to the Snow Leopard partition that would prevent it (Yosemite) from being formatted/overwritten, shouldn't I be able to simply blow away the HD that has Yosemite on it with the Snow Leopard Disk Utility?

If necssary I can pull that drive from the Mac case and format it elsewhere if need be (are blow torches and sledgehammers required?)... or does Yosemite have some evil self-preservation, anti-self-destruct bomb built in? Seriously...how could having Yosemite on a disk prevent that disk form being formatted? I'm more than a little skeptical...

Reply

Answer 8

den.thed

Level 9

77,176 points

May 25, 2015 9:18 PM in response to longtimemacuser666

Guess you'll have to try it that way for yourself.

I have not tried taking an HD back to Snow Leopard from Yosemite, but I did several times from Lion. Again an earlier OS X can not erase and reformat a later OS X, especially one's like Lion, Mountain Lion, Maverick or Yosemite, because of their hidden EFI and Recovery Partitions.

Have a look at the > Google Search: reverting back to an earlier OS X

Reply