virtualbox.org

ThisIsMe wrote:I'm not sure what you mean by a "guest OS".

Yes, a "guest OS" is the VM's OS. Around these parts we call the real PC the 'host' and the VM the 'guest'.

ThisIsMe wrote:I need something which can be dynamically updated, until I flip a switch so that it can't any more.

Think of how you would solve this on a real PC, then apply the method to the VM.

On a real PC, CD's and ISO's can't be written to after they've been made once *. So you can't write to CD's and ISO's inside a Virtualbox guest, which includes Virtualbox's special-feature VISO's, too. ( * some special things were done with CD-RW's back in the day before USB drives became ubiquitous, that could allow one to write to an already-written CD-RW, but sessions had to be closed or very special file systems were needed. Suffice it to say that those probably won't help now.)

On a real PC, hard disks can be written to, and you can then make an ISO out of a folder structure on the hard disk, then test the ISO as a CD or USB stick.

Don't try to write to the ISO you are booting from. Write to the source files that you have copied from the ISO to a hard drive, then make an ISO from the hard drive copy.

ThisIsMe wrote:fth0, are you referring to it not being configured by default to prioritize booting a USB drive first? Well that's easy to fix, or the boot menu can be used.

Yes. I tried to think about your concept from the beginning, and the (UEFI or legacy) BIOS boot menu would be the first possible branching point, followed by the boot manager on the USB stick. Since I would not allow you to configure on of my computers to automatically boot from a USB medium for security reasons, using the BIOS boot menu would be mandatory if I were one of your users. But I see now that I get to the same questions that you already have asked.