How to find which drivers - configure kernel to boot off a USB stick without initrd

Couling · 10-28-2009, 05:58 AM

As a learning exercise I'm trying to build a really simple Linux system. (Grub, kernel, bash [static build]) on a usb stick (unbranded).

I'm having a lot of trouble configuring a kernel that will boot. Every time I get:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

According to what I've already read this is telling me that it cant read the root file system, probably because it doesn't have the right drivers.

If I take an ubuntu kernel and initrd everything works fine, but it needs the initrd otherwise it has the same problem.

How do I find which drivers are missing, or which drivers ubuntu is using to access the device?

Thanks for your time.

hurry_hui · 10-28-2009, 11:48 AM

When configuring kernel for USB pay attention to this section:

USB Host Controller Drivers. This covers module UHCI, OHCI EHCI.

You might also want to enable SCSI (SATA_AHCI), USB Storage as well as Block Devices (i.e., for SD/MMC support)

CMIIW

Couling · 10-28-2009, 07:17 PM

Okay, tried all of those, still have the same problem. Have also tried turning on pretty much everything SATA, USB and SD. Is there a way to take a device (say /dev/sdd) and in some way back-track to find which drivers its using?

hurry_hui · 10-30-2009, 01:10 AM

You can check dmesg or syslog; you might get one from running LiveCD. When I first configured my kernel, I compared some distros in detecting my devices by looking at dmesg and syslog.

ATM, my dmesg shows scsi0 and scsi1 load ata_piix (this is because I use Intel machine) while sr and sd load scsi generic, and scsi CD-ROM.

You can also check available controllers such as USB UHCI, USB2 EHCI, SATA IDE, from the machine via 'lspci'

HTH

ssenuta · 10-30-2009, 09:04 PM

Most usb-stick are a single type 06 partition formated vfat (fat16 fat32) & to boot them you must have the vfat driver built into your kernel. To check this try mounting your usb-stick & once mounted run the "df -T" command to display the filesystem type.

mount -t vfat /dev/sdd1 /mnt/misc
--or--
mount -t auto /dev/sdd1 /mnt/misc
df -T

Of course you can always repartition your usb-stick to a Linux type 83 partition & then format it to ext3 if you already have ext3 built into your kernel. But, regardless the filesystem format you have on your usb-stick must have a driver built into the kernel or you are forced to pre-load that driver via an initrd.

I hope this helps & good luck.