virtualbox.org

On my 64-bit Linux host, I can not install the WinXP guest additions. Clicking Devices --> Install Guest Additions does not mount the virtual cd within the guest. I also tried to Devices --> Mount CD/DVD-ROM This also will not mount the guest additions iso. (Although I could mount all other iso images I tested.)

From within the host this worked:
mount -o loop -o ro /opt/VirtualBox/additions/VBoxGuestAdditions.iso /mnt/iso

So as a work-around, I used ftp to transfer VBoxWindowsAdditions-x86.exe to the guest. Then I executed that file on the guest. Now everything (except mounting the guest additions iso) works.

What is 'special' about the guest additions iso within a VirtualBox guest?

Usually all you need to do is click unmount the cd first and then click install guest additions.

I tried that. Also, the little cd icon on the bottom of the guest screen was grey. I assume that means there was no attached cd.

The strange thing is that several other iso images mounted and unmounted without issue. It is only the GuestAdditions iso that was giving me trouble.