UUID soup

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markfilipak
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UUID soup

Post by markfilipak » Fri Jun 07, 2019 2:24 am

This is the Newbie section, and this doesn't seem like a Newbie question, but it doesn't seem to fit in any other section.

In my Mint guest OS, I've attached a virtual USB stick to which VBox assigned a UUID of '88547b35-b43b-4fac-8671-b55688d6deff'. Linux mounted it automatically to '/media/mark/88c55591-ccd9-422c-8d91-0d23bc2bc353' ...another UUID.

Here's a question that I bet no one can answer: Where did the UUID, '88c55591-ccd9-422c-8d91-0d23bc2bc353', come from?

gm10
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Re: UUID soup

Post by gm10 » Fri Jun 07, 2019 4:19 am

UUID vs PARTUUID
Tune up your LM 19.x: ppa:gm10/linuxmint-tools

markfilipak
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Re: UUID soup

Post by markfilipak » Fri Jun 07, 2019 4:43 am

gm10 wrote:
Fri Jun 07, 2019 4:19 am
UUID vs PARTUUID
Thanks, but no cigar. I discovered the answer about 10 minutes ago.

VirtualBox communicates with the Guest Additions via a slow-speed channel. Upon boot of the virtual machine, the VBox Manager sends a message to the Guest Addtions that names all the mount points of virtual hard disks attached to the virtual machine. So '88c55591-ccd9-422c-8d91-0d23bc2bc353' comes from VBox, not from Linux or from any partition.

The impact of that knowledge is that a person should not rename a mount point in the guest OS. I haven't found a way to rename mount points in VBox.

gm10
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Re: UUID soup

Post by gm10 » Fri Jun 07, 2019 4:58 am

What have the Guest Additions got to do with anything? You don't even need them installed to attach virtual media.

But now I understand what you were confused about. The original UUID you were talking about is the one from VirtualBox' Virtual Media Manager, not the one from within Linux. Naturally that one will be different, that's only being used by Virtual Box itself to identify virtual media and associate them with virtual machines.

Within the guest OS you are free to change your mount points to whatever you like, it is nothing to VirtualBox and certainly not to the (unrelated) Guest Additions. In a Linux Mint guest you can do so, for example, via the Mint menu > Disks tool (unmount > edit mount options > remount).
Tune up your LM 19.x: ppa:gm10/linuxmint-tools

markfilipak
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Re: UUID soup

Post by markfilipak » Fri Jun 07, 2019 5:14 am

gm10 wrote:
Fri Jun 07, 2019 4:58 am
Within the guest OS you are free to change your mount points to whatever you like, it is nothing to VirtualBox and certainly not to the (unrelated) Guest Additions. In a Linux Mint guest you can do so, for example, via the Mint menu > Disks tool (unmount > edit mount options > remount).
I don't think so. Now, it is possible that Guest Additions may track changes to the name of the mount point directory and update the virtual machine store, but I'm not going to take that chance. I can definitely tell you that the name of the mount point directory is definitely, absolutely, without a doubt passed to the insides of the VM (to the Guest Additions) by the VBox Manager as the VM is instantiated.

gm10
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Re: UUID soup

Post by gm10 » Fri Jun 07, 2019 5:20 am

Who am I to stand in the way of a man's beliefs?

So don't mind me when I'm doing this:
vbox_mount.png
I have a feeling you're talking about shared folders instead of virtual media, because that would actually be something the guest additions handle.
Tune up your LM 19.x: ppa:gm10/linuxmint-tools

markfilipak
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Re: UUID soup

Post by markfilipak » Fri Jun 07, 2019 4:09 pm

gm10 wrote:
Fri Jun 07, 2019 5:20 am
Who am I to stand in the way of a man's beliefs?
If I'm interpreting you correctly, then UUID/GUID '88c55591-ccd9-422c-8d91-0d23bc2bc353', which is the mount point directory for the VHD I've named 'Palemoon portable (Linux).vhd', was given that UUID/GUID by the Mint guest?

gm10
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Re: UUID soup

Post by gm10 » Fri Jun 07, 2019 4:15 pm

Naturally. VirtualBox provides only the container, the partition table (which is what contains the UUIDs) that gets written onto the drive is up to the guest.
Tune up your LM 19.x: ppa:gm10/linuxmint-tools

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