Why set the type as vboxfs while you did format /dev/sda1 as of type linux?
The right command would be just:
Code:
mount /dev/sda1 /mnt
But this will fail anyway because you did set the partition type but not yet (I guess) put a filesystem in it.
So just type "setup" and let the Slackware installer do all that for you. It will ask you which partition you want to use as installation "target" (and propose you /dev/sda1 that you will accept) then which filesystem you want (the default ext4 is good enough).
Also, I hope that you meant 8GB for /dev/sda1, not 8Mb. Anyway if you really want to use Slackware I suggest that you set it to at least 10 GB to be able to store your data and add third party software.
Finally, I suggest that you do some reading before installing, so go to
SlackDocs now.
PS the mount command with vboxfs is for a shared folder, e.g. containing files in your Debian system that you would like to access from your Slackware system in the virtual machine. You will need to have completed the installation of Slackware in that virtual machine to be able to use this feature: do
not do that from the installer, as it's just a tentative system that live in RAM till you reboot or shutdown the machine, then disappears.
And, from your installed Slackware system, you won't be mounting a partition (as is the case with an usual mount command) but somehow "remount" a Debian's folder in Slackware when using shared folders.
I hope I did shed some light, but else feel free to ask more questions.