24.11.2020 15:31, Brian J. Murrell пишет: > On Mon, 2020-11-23 at 10:06 -0500, Brian J. Murrell wrote: >> I am using grub2-pc version 2.0.4 as packaged by Fedora 32. >> >> I am trying to get a serial console working using a USB->Serial >> dongle. >> >> I understand that in order to do that I need to use GRUB's native >> drivers as the moment GRUB tries to use the USB hardware it loses use >> of the BIOS disk drivers. >> >> Working at a command-line for the moment, to figure out the steps I >> do: >> >> grub> insmod nativedisk >> grub> nativedisk >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> error: ../../grub-core/net/net.c:1547:disk `hd0,msdos1' not found. >> >> and then am left with a frozen grub> prompt. Even ALT-CTRL-DEL >> doesn't >> work. > > Maybe what is really quite relevant but had only occurred to me this > morning is that the disk that the machine is booted on is a SD-Card > which is connected by USB: > > Bus 001 Device 004: ID 0bda:0159 Realtek Semiconductor Corp. RTS5159 Card > Reader Controller > > I suppose nativedisk cannot support that as it needs the USB drivers > loaded also, (at least) and the moment you load those, you lose access > to the disk through the BIOS. > > Can the USB modules be loaded but left in an "un-activated" state so > that they don't interfere with BIOS access to the USB disk? Once they > are all loaded, then nativedisk can "activate" the USB drivers (which > are already loaded, but inactive) to get access to the disk. > > Is this possible? > > But maybe this is what is supposed to happen already? >
Yes, this is exactly what happens. > https://wiki.debian.org/BootUsbWithGrubRescue#Booting_a_flash_drive_with_an_image_file_written_to_it > #3 says: > > Use the nativedisk command to tell Grub to load its native disk and > USB drivers. > > Which seems to be implying that the nativedisk command is loading the > USB drivers also. > By default nativedisk command loads the following modules (on x86): pata,ahci,usbms,ohci,uhci,ehci you can also give list of modules as arguments to nativedisk. grub first reads all the modules in memory using platform disk support (i.e. BIOS on i386-pc), then initializes them from memory copy. Then it tries to find device with $prefix and $root UUIDs using new drivers.
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