Option key reboot to select new startup disk often doesn't work

Question

Level 2

248 points

Option key reboot to select new startup disk often doesn't work

I've been doing a lot of work on a couple of bootable hard drives, and often have needed to boot into them, to do the work.

I'm on an older iMac (late 2013) running Mojave, and the hard drives are Samsung T5 SSDs (also on Mojave).

9 times out of ten, the Option key reboot will not bring up the disks for me to select.

Things I've done to try to fix it. Reset the PRAM. Worked once. Unplugged the hard-drives, and plugged them back in again. Worked once. I've tried making the T5 the startup disk in System Preferences. Sometimes works, but often the iMac will just go ahead and boot into the internal drive.

What does seem to work is unplugging the power cable into iMac for a short while, and plugging back in, but that is a bit inconvenient to keep doing that.

I head that using an apple remote on startup can help, (press menu key at same time), but my remote hasn't been used in years and the battery is flat, got a new battery coming today, so yet to try that one.

My theory is that, when I'm booted into internal drive, and the external drives can be seen sitting on the desktop so it looks like everything is fine, for some reason they are not being 'seen' when I try the Option key start up, so the iMac just goes and boots into the internal drive.

Does anyone have any ideas?

Tnks

Posted on Apr 30, 2022 1:26 AM

Reply

Answer 1

Top-ranking reply

PRP_53

Level 10

90,955 points

Apr 30, 2022 7:09 AM in response to Kathykate

Suggestion from Observations on these Apple Support Community Forums.

Have Only the Bootable External Drive attached when starting and using the Option Key.

For some reason, having more than one external drive attached @ a cold boot-up - confuses the computer

Reply

Answer 2

Apr 30, 2022 7:43 AM in response to Kathykate

I have a Mac mini 2018 with the T2 chip which somewhat complicates external boot (you have to enable it via a detour to Recovery mode in the first place and it seems sometimes the T2 chip has its own ways).

I have a few external backup and test disks and volumes. Usually Option-boot works well. Mac's born-again startup chime makes timing the Option boot easier but a cold-boot with Option is slightly more reliable. A Bluetooth keyboard seems to work well even in this scenario.

I have one external disk with about 10 bootable macOS 10.14.6 - 11.6.5 - 12.3.1 backups and test volumes and usually Option-boot works well even with that monster. But rarely the Option-boot stalls to a black screen. That is easily fixed with forced shutdown and a cold Option-boot.

Reply

Answer 3

Kathykate Author

Level 2

248 points

Apr 30, 2022 11:39 PM in response to BDAqua

I have.... but maybe not for long enough. I will have to do an experiment and leave for about 10 mins. But that doesn't explain why, on removing the power plug from Mac, and doing option boot, I get the bootable disks come up really quickly. Or does it? I am fumbling around in the dark.

Luckily I've just about come to the end of fiddling around with these externals, and won't need to switch boots so much. I was, however, considering having one of them as my permanent startup drive, as my Mac is 'vintgage'. And I do like to get things working as they should, so I will probably continue with this quest for a while longer.

Reply

Answer 4

Kathykate Author

Level 2

248 points

Apr 30, 2022 11:41 PM in response to Matti Haveri

Stalling to a black screen is what happens to me. And then I have to press power key to force shutdown. What do you use for forced shutdown exactly? Power button, or keyboard control/command/eject keys?

Reply

Answer 5

May 1, 2022 2:02 AM in response to Kathykate

> What do you use for forced shutdown

Press Power button until the Mac mini 2018 shuts down.

I suspect that it sometimes stalls at the black screen (before Apple logo should appear) when initialising or searching EFI boot or something like that. I guess fsck and Spotlight come somewhat later into play (sometimes after a very rare crash it seems fsck is doing its checks for a while in later boot process).

Reply

Answer 6

Kathykate Author

Level 2

248 points

May 2, 2022 12:50 AM in response to PRP_53

I'm marking P.Phillips as the correct answer, although all answers were very helpful and may help others. Having finished with my fiddling with the two T5 externals, one has now been locked away in a safe place. So today I did an option key/boot with just one T5 plugged in and it worked immediately, and I could choose either the T5 or the internal drive, so I'm thinking in my case my old 2013 workhorse iMac WAS getting confused by having two T5s plugged in. So to recap, if you are having the same problem, either just have one ext. HD plugged in, or unplug your iMac for 30 secs before doing the option key/boot (which also worked for me, but was tiresome).

Reply