Installing Sonoma on external drive, not enough space on internal drive??

[imrazor]

A picture will probably explain my problem better than my incoherent ramblings...

As you can see the installer is telling me that I don't have enough space on my internal(boot) volume to install Sonoma on a disk that has 700GB free. What the heck?

 

[rm5]

Here's my guess: it says the current boot volume needs an additional 2.54 GB not the external—so just to be safe, I'd free up another 16-20 GB if possible on Macintosh HD—so you'd have roughly 32 GB available. The reason being that you need to download additional components to install it, even to an external drive.

 

[haralds]

You are running low on your main drive even for normal use. I like to keep 20% of a drive free but never go below 10%. macOS does not handle low space on disk gracefully.

 

[imrazor]

I did reduce the size of my boot volume by ~10GB or so, and finally got Sonoma installed on an external volume.

My best guess is that a bootloader needed to be installed, but 2.5GB is HUGE for a bootloader. So I'm not entirely sure why that is a necessary requirement.

It's all working now, though.