RE: Qemu doesn't detect hard drive

[Aijaz.Baig@protonmail.com]

Thanks for the tip Pete. It is always tiny tidbits like these that can waste hours of time for someone coming from x86 😉. 

Ok I changed the command line and it looks like this now:
sudo qemu-system-arm -m 1024M -M vexpress-a9 -D qemu.log -sd armdisk.img -kernel buildroot-2019.02.5/output/images/zImage -dtb buildroot-2019.02.5/output/images/vexpress-v2p-ca9.dtb -append "root=/dev/ram console=ttyAMA0,115200 kgdboc=kbd,ttyAMA0,115200 ip=dhcp nokaslr" -initrd buildroot-2019.02.5/output/images/rootfs.cpio -nographic -net nic -net bridge,br=mybridge -s

I am looking at 'dumping' a Debian like rootfs on the MMC and then use that as the default rootfs instead of the busybox one. Is there an easy to follow guide that you can point me at?  Would save me a couple hours. Also, merely specifying that partition as the kernel 'root' parameter should suffice right?

-----Original Message-----
From: Peter Maydell <peter.maydell@linaro.org> 
Sent: Friday, April 3, 2020 1:10 PM
To: Aijaz.Baig <Aijaz.Baig@protonmail.com>
Cc: qemu-devel@nongnu.org
Subject: Re: Qemu doesn't detect hard drive


On Fri, 3 Apr 2020 at 06:18, Aijaz.Baig <Aijaz.Baig@protonmail.com> wrote:
> I would now like to add a hard disk for persistent storage and then 
> transfer control from busybox initrd based rootfs over to the full 
> fledged version offered with Linux. So I add it to the command line
>
> `sudo qemu-system-arm -m 1024M -M vexpress-a9 -D qemu.log -drive 
> if=none,format=raw,file=disk.img -kernel 
> buildroot-2019.02.5/output/images/zImage -dtb 
> buildroot-2019.02.5/output/images/vexpress-v2p-ca9.dtb -append 
> "console=ttyAMA0,115200 kgdboc=kbd,ttyAMA0,115200 ip=dhcp nokaslr" 
> -initrd buildroot-2019.02.5/output/images/rootfs.cpio -nographic -net 
> nic -net bridge,br=mybridge -s

This command line creates a "drive" object but doesn't plug it in to anything (it's like asking QEMU to model a board, with a hard drive sat next to it on the desk but no cable between them :-))

More generally, the vexpress-a9 board does not support hard disks.
This is because the real hardware we're modelling here has no disk drive interfaces and no PCI or similar bus that you could plug a scsi controller into. The best it can do for storage is an SD card emulation, which works but the performance is not great.

thanks
-- PMM