OS Sierra Security Update Problem: Startup Disk Changed To Another Drive

[Mojo1]

Today (4/6/18) I performed the latest security update for OS10.12.6 Security Update 2018-00 bundled with Safari and iTunes updates.

After restarting, it was apparent that my 2012 Mac Mini that normally boots from an external USB 3.0 SSD was instead booting from an old OS living on a partition on a Firewire 800 external drive. The OS was circa 10.6. . .

When I checked my startup drive options while in that state, the external USB 3.0 SSD was not available or even listed as an option.

So I restarted in Safe Mode and the SSD reappeared and was the default startup drive. Just to be sure, I reselected it and then ejected the external drive with the various bootable volumes and powered it down.

After I restarted again, I powered up the FW800 external drive because it contains files that my apps access. Things appear to be working but I have not tried restarting with the external FW800 drive powered-up.

BTW, the OS Sierra Security update that I applied is not showing up on my App Store list of updates done within the past 30 days. However, both iTunes 12.7.4 and Safari 11.1 that were bundled with it show up, with an install date of March 31, 2018 instead of April 6, 2018.

I'd appreciate insights/feedback about what, if anything, I should do next. . . At some point later today I'll give the restart a try, since apparently I can recover from it if the same thing happens again.

 

[Fishrrman]

Can't you just open the Startup Disk pref pane and "change it back" to the proper startup drive?

Was this a "one-time occurrence?"
If so, I'd just "set things right".
If it doesn't happen again, don't worry about it.

 

[Mojo1]

The Mac Mini booted up normally this morning and has run all day long without a mishap. This appears to be a weird one-time thing. . .

One reason I posted the incident was the complete absence of the boot drive from the startup disk options. It only showed up after I booted into Safe Mode.

I usually run Apple security updates without a second thought. But after this experience I am going to wait a few days and make sure there aren't any problems associated with an update.

 

[DeltaMac]

I expect that the security update may have "un-set" the boot settings. When you restarted, your Mac chose whatever random startup volume mounted first. If it was something older, like 10.7, then a newer drive, functioning under Sierra, might not be visible in Startup Disk. I have seen this happen. That last Sierra updates allow for APFS format drives, and those certainly won't show up as bootable in Lion, etc, and maybe not even mount at all.
But, rebooting your Mac, holding the option key, should show your normal boot drive, which you can select there, and continue to boot to your normal system. And, you would make sure that is a good selection in the Startup Disk Pane.
I bet it was NOT highlighted when you first opened that pane. Click on your normal boot drive, just to make sure it is properly selected.
Here's what I would do to help make sure that won't happen on next restart:
Do an NVRAM reset: Restart, holding Option-Command-p-r. You should hear a boot chime sound. Keep holding the same 4 keys until you hear the boot chime two more times, then release the keys except for Option, so you can choose your boot drive. This reset WILL reset the boot drive, so when you have booted to your desktop, go back into System Preferences/Startup Disk, and select your boot drive, so it is highlighted. Close System Preferences, and that should take care of the default boot disk now. You can also set your system volume to whatever (as that is reset, too)

 

[Mojo1]

DeltaMac, thanks much for your reply. . . The security update not only affected the boot settings, it also screwed up a few login item preferences as well. I've never had this happen before with a security update. Major OS update, yes indeed!

So far the desired boot drive has been used, so I think that the NVRAM reset isn't required.

Question: You write about the boot and system volumes as if they can be different volumes. Come again? I assume that the boot and system volume is one and the same. . .

 

[DeltaMac]

...
So far the desired boot drive has been used, so I think that the NVRAM reset isn't required.

Question: You write about the boot and system volumes as if they can be different volumes. Come again? I assume that the boot and system volume is one and the same. . .

Just my little take on the way Macs boot.
If the startup disk has been reset, and, that is the setting that determines what boot drive is the default - then if you do nothing, the Mac defaults to the first boot partition that is available. This may be the same as your internal drive. If you have (like I do) several different partitions on the internal drive (3 different OSes), and, in addition, have an external hard drive like I have with 15 (!) partitions, all with various bootable systems, and the hardware doesn't have a default to use, then it's hard to tell what partition will be used for booting. However, if you have the same hardware configuration, you do often see that one bootable system seems to be the "unselected" default. I'm pretty sure it will be the first one that is recognized by the Mac during startup.
So, I have the "normal" boot volume, the one that is usually used, and the one where I do all my work, whatever it might be. The quickest way to know which volume that is the default, is to choose that volume in the Startup Disk pref pane.
And, to answer your question (in a roundabout way), the boot volume is the one that you are booted to. That has your system on it, so would be the system volume. In my situation, if I look in the Startup Disk pane, I might see up to 20 possible selections, some of which my Mac cannot boot successfully. But, they are presented as possible choices. I just have to know that my 2012 mini can't possibly boot to an OS X 10.4.6 system that happens to be on that external drive. I look for my "normal" boot drive, and make sure that is highlighted. I experiment all the time with different system volumes, trying to set up to "force" booting on non-compatible systems. Those I refer to as system drives, because they have systems installed. They are not necessarily "boot" drives, unless they are attached to Macs that will likely boot to those particular volumes.
Yeah, I know, doesn't make a lot of sense.

But... In the last couple of macOS versions, after I install system updates, I have got into the habit of doing an NVRAM reset, if only to unset the default drives. (I want to make sure that update has not changed the defaults.) Then boot to my normal system, and set that boot drive in Startup Disk.
Because --- I want to make sure about that setting. It takes less than 2 minutes, and cannot possibly harm anything.

 

[Mojo1]

Now I get it. . . Those bootable volumes on my external drives are SuperDuper! backups. A few of them need to be trashed. . . I no longer need the bootable clone of my 2006 iMac Core2Duo!

The first thing I need to do is buy a larger USB 3.0 SSD. . . I thought that a 250GB SSD would be sufficient but my calculations were off. A 500GB will do it but I need to go through my notes and make sure I know how to do it. I've considered installing an internal SSD but it seems to be a tad tough for my taste. Installing an SSD in a 13" MBP is a piece of cake in comparison.

Do you have a suggestion for a reasonably priced powered USB 3.0 hub? I'm done unplugging USB cables from the back of my Mac Mini!

 

[DeltaMac]

My favorite is Anker brand, but then I also like Monoprice, mostly because they are often best price, and usually good performing.

How many ports do you need on a hub? Monoprice has a good price on 4, or 7, or 10 ports, individually switchable ports, too.
https://www.monoprice.com/product?p_id=21787

 

[Mojo1]

I'm familiar with both brands but I would not have thought of Anker for a USB hub. I'll need to figure out how many ports I need; most likely 4 will do the trick. I'll check the Monoprice link first. Thanks much!