Problem booting from external Thunderbolt drive

[Flaming Gerbil]

First time trying this with my M1 Macbook Air (256GB internal too full).

Went through the install process successfully. Booted off the external no problem. Used all day, then shut down.

Next morning, MB would not start off the external, but brought me to the boot drive selection screen. I selected the external, restarted, and...right back to boot drive selection screen.

After trying a bunch of things I figured out that the Data partition of the internal boot drive was not mounting. In order to mount it, I open Disk Utility, select it, hit mount, and then it wanted authentication. I authenticate, restart, and THEN it boots from external.

So I guess the internal Data drive needing authentication every time is the issue. I tried saving user pw after authenticating, but it doesn't stick.

Anyone know why this happens and/or how to fix?

 

[DeltaMac]

Did you enable File Vault on that external drive? You would then need to authenticate to unlock the drive. Turn off File Vault on that external. That's the fix.

 

[Flaming Gerbil]

Did you enable File Vault on that external drive? You would then need to authenticate to unlock the drive. Turn off File Vault on that external. That's the fix.

I did not. Checked FileVault in settings--it's not on. Also wasn't on for the internal.

As I said, only seems to be the internal drive Data partition that wants auth.

 

[Bigwaff]

As I said, only seems to be the internal drive Data partition that wants auth.

The internal drive is encrypted with a different encryption key than the external boot drive. Makes sense you would need to provide a "password" to decrypt the volume before it can be mounted.

 

[Ray2]

Makes no sense. I have an M1 Aiir. Boot off an external frequently. Scheduled to boot off the external at times. Been doing it for years and never seen this. Though I have seen it when trying to clone a boot drive with Superduper. I use the internal for hours and all is fine. I go to clone and it fails. Drive not available. Look in DU and the data volume (2tb, contains all my data) isn’t mounted. Even though I’ve been using it all day. That was under Monterey. Pretty sure I have not seen it with Sonoma. You running Monterey?

 

[Flaming Gerbil]

You running Monterey?

Sequoia

 

[wonderings]

No answers but I am curious as to why you would boot off an external because your internal is full? Seems like it would be simpler to move all that is taking space on your internal to an external and keep the boot on the internal drive. The opposite seems like you have basically made it not usable as a laptop.

 

[chabig]

The best instructions for creating an external boot drive are here:

Create an external bootable disk for Apple silicon and Intel Macs

Two important catches that can cause a macOS installation to fail in Apple silicon: using the DFU port, and not setting up ownership correctly. Both are explained here.

eclecticlight.co

 

[Flaming Gerbil]

The best instructions for creating an external boot drive are here:

Create an external bootable disk for Apple silicon and Intel Macs

Two important catches that can cause a macOS installation to fail in Apple silicon: using the DFU port, and not setting up ownership correctly. Both are explained here.

eclecticlight.co

Thanks. Didn't know that there's a DFU TB port and you shouldn't use it for a bootable external.

 

[Flaming Gerbil]

No answers but I am curious as to why you would boot off an external because your internal is full? Seems like it would be simpler to move all that is taking space on your internal to an external and keep the boot on the internal drive. The opposite seems like you have basically made it not usable as a laptop.

Didn't want to have to worry about my Applications and Library folders filling up.

But, given the problems I'm having, and the fact that my Sabrent Rocket XTRM+ drive gets XTRMly hot, I'm going to be reverting back to the internal and move the stuff I can to the external.

 

[chabig]

Thanks. Didn't know that there's a DFU TB port and you shouldn't use it for a bootable external.

I just learned that a few weeks ago when this article was written. And still I didn't think to mention it. I'm glad you read the article.

 

[Fishrrman]

OP wrote:
"given the problems I'm having, and the fact that my Sabrent Rocket XTRM+ drive gets XTRMly hot, I'm going to be reverting back to the internal and move the stuff I can to the external"

I predict that your own experience is going to be echoed by many more owners of m-series Macs who "bought too small" in terms of the internal SSD, thinking that they could "work around it" by booting externally.

With Intel, this wasn't a problem. I booted and ran my 2012 Mini for SIX YEARS from an external SSD, from the very first day I took it out of the box. It's still sitting on "the back table" now, and still booting from an external SSD.

But... Apple Silicon has changed that.
It's getting more problematical to boot/run from an external drive.
Apple keeps tossing "blocks" into the pathway.

 

[theorist9]

Are you running the current version of Sequoia (15.3.1)? The ability to make bootable backups was killed in Sequoia 15.2, but restored in 15.3.

Though I should also let you know that, while bootable backups are a great convenience, Apple made them tricky to implement several OS's ago. Thus while you can get them to work, don't count on them being as robust as they used to be.

The backup strategy that matches Apple's current OS's is to only backup what's outside the SSV (signed system volume). That gives you all your data, apps, and settings, but it's not bootable. That's the default for CCC.

macOS Sequoia 15.2 isn't allowing third-party utilities to make bootable backups

The developer of SuperDuper! says what they think is a bug in macOS Sequoia 15.2 has inadvertently broken how the app can create bootable backups — however, it may not be accidental at all.

appleinsider.com

macOS Sequoia 15.3 Update Fixes Third-Party Bootable Backups Failures

macOS Sequoia 15.3 appears to include a remedy for a bug that prevented third-party backup utilities, like SuperDuper from creating bootable backups.

www.mactrast.com