Have OS X on 2 HDDs, problem performing Software Update

[Luba]

I have OS X without any 3rd party app's on another partition on another HDD as a kind of backup in case there's any conflicts or problems with the main everyday OS X I use. I needed to run Software Update on the stripped down OS, so while running on the everyday OS I clicked restart and held down the Option key. This allowed me to select the stripped down OS and boot into that OS. I should have gone into System Preferences, Startup Disk to restart into the stripped down OS, and doing that would have avoided my issue!

Anyway . . . so now I am booted into the stripped down OS, I run Software Update and it has to restart to complete the Update, BUT the everyday OS is the one that's still selected as my startup disk in System Pref. Software Update restarts and initially it looks like I am in the stripped down OS version as the dock icon setup looks like it's for the stripped down OS, but as I click around the dock icon setup changes to the one on the everyday OS. I open up the App folder and there are many 3rd party app's in it so obvious I am running using the everyday OS.

So when Software Update restarted did it complete the Update on the stripped down OS? I know under System Pref, the everyday OS was selected, but how did the Mac restart me into the everyday OS without asking for my username and password? Finally, do you think I have any problems with what has happened? I now know I should have gone into System Preferences, Startup Disk and selected the stripped down OS to restart into the stripped down OS, and doing that would have avoided this whole problem. Any help will be appreciated! Thanks.

 

[ActionableMango]

I would temporarily pop out one of the OS drives to prevent conflict. Hopefully you can then resolve with a new attempt at updating. Then, I'd pop out the fixed on and put the other OS drive back in and try to fix that one separately too.

 

[nufanec]

It will be fine. Your "every day" OS has not been touched. The install is done at shutdown not boot. Next time you start up to the back up OS disk it will finish up anything it needs to.

 

[Luba]

But why did the desktop initially look like I was in the backup OS, as I clicked around the desktop transformed into the everyday OS desktop. Also since I am booting from the backup OS to the everyday OS, it didn't ask for my everyday OS user and password??

It makes sense, so when I was in the backup/stripped-down OS and when I then clicked restart to finish the update, it installed the update on the backup OS, then booted me up in the everyday OS.

An Apple genius suggested I download 10.6.7 Combo Update and install on both the everyday and backup OS. Could this cause problems, or just un-necessary in your opinion.

He is guessing that when I was in the backup OS installing the update and when it required a restart it installed on the everyday install, as I had the startup disk pointing to the everyday one. He said it would be impossible for Mac to restart/boot into the backup OS, then "jump" to the everyday install, but had no explanation why initially after restart the desktop looked like the backup OS then after a few clicks/minutes using Mac transformed itself to look like the everyday OS.

It will be fine. Your "every day" OS has not been touched. The install is done at shutdown not boot. Next time you start up to the back up OS disk it will finish up anything it needs to.

 

[Krevnik]

As long as installs aren't touching the NVRAM (hint, they don't unless it is a hardware firmware update), the two installs don't touch each other.

What happens during an update is that the machine swaps out the active files (kernel, drivers, etc) with the new ones, moving the old ones to a temporary location on the startup drive (or simply deleting them if it is an option). On reboot, the machine is now running on the new versions of these files, and it can safely delete the old ones.

The real reason for the reboot is that it can be difficult to swap out running code without heavily impacting something, especially if it involves the kernel or drivers. The easiest answer is to require a reboot to ensure the system runs on the updated code.