On Fri, Mar 4, 2016 at 3:56 PM, Kristof Provost <kristof@sigsegv.be> wrote:

On 04 Mar 2016, at 23:50, Patrick <plafratt@gmail.com> wrote:
Thanks for the response. I had seen that StackOverflow post and done that a couple of days ago. I was hoping there was another answer, since I wouldn't be able to do that if I weren't using QEMU.

If you weren’t using Qemu I’d point you at netconsole. The first step in debugging panics is always to figure out what the panic is.

When I looked at the output from QEMU a couple of days ago, the kernel was saying that it couldn't find a device to mount with the root filesystem. So I generated an initrd image on the host Linux system, and I used that on the guest which got me to a BusyBox prompt. But this was totally a hack, since I didn't even know if getting an initrd image was really the next thing I needed to do. I was hoping someone might be able to point me to something that might explain what to do to get the kernel to mount a device with the root filesystem.

You want to pass the ‘root=/dev/foo’ option to your kernel. Obviously change /dev/foo into whatever device you’re booting from.

Regards,
Kristof

Ok, thanks. I will try to look into netconsole.

I had tried changing the "root" option. I had noticed that the QEMU output showed the kernel printing out this:

[ 4.312088] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6

[ 4.322029] Please append a correct "root=" boot option; here are the available partitions:

[ 4.327850] 0100 65536 ram0 (driver?)

[ 4.337399] 0101 65536 ram1 (driver?)

[ 4.345170] 0102 65536 ram2 (driver?)

[ 4.345691] 0103 65536 ram3 (driver?)

[ 4.346251] 0104 65536 ram4 (driver?)

[ 4.346825] 0105 65536 ram5 (driver?)

[ 4.347442] 0106 65536 ram6 (driver?)

[ 4.350055] 010a 65536 ram10 (driver?)

[ 4.352624] 010b 65536 ram11 (driver?)

[ 4.353597] 010c 65536 ram12 (driver?)

[ 4.354517] 010d 65536 ram13 (driver?)

[ 4.354977] 010e 65536 ram14 (driver?)

[ 4.358393] 010f 65536 ram15 (driver?)

[ 4.359420] 0b00 1048575 sr0 driver: sr

[ 4.360499] 0800 102400 sda driver: sd

[ 4.367898] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

I hadn't noticed "sda" before. So I tried pointing root at this. Then I got this:

[ 4.375721] List of all partitions:

[ 4.383491] 0100 65536 ram0 (driver?)

[ 4.386418] 0101 65536 ram1 (driver?)

[ 4.388736] 0102 65536 ram2 (driver?)

[ 4.390931] 0103 65536 ram3 (driver?)

[ 4.391266] 0104 65536 ram4 (driver?)

[ 4.391726] 0105 65536 ram5 (driver?)

[ 4.392812] 0106 65536 ram6 (driver?)

[ 4.393340] 0107 65536 ram7 (driver?)

[ 4.393932] 0108 65536 ram8 (driver?)

[ 4.394906] 0109 65536 ram9 (driver?)

[ 4.396283] 010a 65536 ram10 (driver?)

[ 4.399212] 010b 65536 ram11 (driver?)

[ 4.400067] 010c 65536 ram12 (driver?)

[ 4.401832] 010d 65536 ram13 (driver?)

[ 4.402775] 010e 65536 ram14 (driver?)

[ 4.403572] 010f 65536 ram15 (driver?)

[ 4.404046] 0800 102400 sda driver: sd

[ 4.412148] 0b00 1048575 sr0 driver: sr

[ 4.413323] No filesystem could mount root, tried: ext3 ext2 ext4 vfat fuseblk

[ 4.415310] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(8,0)

So, I think maybe now the kernel is missing some things it needs on /dev/sda. Right now, I don't think there is anything on it other than the bootloader. Do you happen to know where I can find what the kernel needs to proceed?

Thanks,

Patrick