Re: Official way of enabling USB on grub 2.02?

[adrian15]

El 09/01/15 a las 07:10, Andrei Borzenkov escribió:
> В Fri, 09 Jan 2015 02:45:40 +0100
> adrian15 <address@hidden> пишет:
>
> > I'm having problems using my old commands (from grub 2.00) for enabling
> > USB when using grub 2.02. I also think that in grub 2.00 they did not
> > work completely ok.
> >
> > Anyways, the question is:
> >
> >     How one is supposed to enable Grub2's USB support when using: 2.02?
> >
> > I'm currently doing my tests with Debian Jessie: 2.02~beta2-19 version.
> >
> >
> >
> > These were the original commands:
> >       insmod ohci
> >       insmod uhci
> >       insmod usbms
> >       update_paths
> >
> > The first one says:
> > error: disk `hd96' not found
>
> USB drivers work with hardware directly and so conflict with BIOS
> for hardware access. For this reasons as soon as you load any driver
> that does it grub will stop calling into BIOS. As by default grub is
> using BIOS for hard drive access, those devices no more work.
Ok. I can understand it.

But why every command at grub shell (even: echo $grub_prefix) after 
running: "insmod ohci" always says:

error: disk `hd96' not found.

As I say, this is in grub shell, not running commands from a menu. 
Although originally I have come to the shell from a menu thanks to 'c' key.

> > and I cannot longer use my custom grub menues (The Super Grub2 Disk menus).
> >
> > Thank you for any clue on how to enable USB support in the correct way.
>
> grub2 has command "nativedisk" that will try to switch from platform
> firmware driver (BIOS) to native hardware disk drivers. This may give
> you back your disks, but under different names. Note that some commands
> will not function, e.g. there is no way to chainload something unless
> using BIOS.
nativedisk in my virtualbox test also gives me:

error: disk `hd96' not found.

With Grub 2.00-22 (from Debian) I think that USB did not work as I was 
expecting (just adding a new drive for usb devices detected. I know that 
you are explaining right now that the current devices are being replaced 
by new ones. But in 2.00-22 version, at least, I did not give that: 
error: disk `hd96' not found error.).

> Could you give more details what exactly are you trying to do?

As you might imagine what I wanted to achieve in first place is to add 
usb based devices as grub additional devices so that I can loop between 
usual grub devices and the usb ones in order to find OSes to boot.

If, as you explain, the cdrom which it's accessed via BIOS is no longer 
there, then, I guess that I would have to convert (I mean to build it in 
first place and boot it) the SG2D disk into a memdisk device which I 
hope it does not get disconnected when "insmod ohci" is run.

And then, well, try to load the usb grub devices.

Summary:

Given a grub shell, who am I supposed to load usb drives and its devices?

What should it happen when I do it? If there is an usb hard disk. And if 
there is not?

Can I, somehow, unload or undo the usb drives, without having to reboot?

And how's the best way to keep the original grub device intact? memdisk 
device?

By the way, we have other commands for enabling raid devices, lvm 
devices, luks, etc,... and these sort of drives disappearing thing does 
not happen. Just it helps you.

I'm using Virtualbox 4.3.20 r96996.

Thank you!

adrian15
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