Hi,

I need help for creating a bootable diskimage. I have a filesystem and a kernel included in a file rootfs.ext2 (or rootfs.tar, I have both).

I made a bootable image by using dd,fdisk and mkfs.ext2, but at the end the kernel allways complains that the root filesystem could not be mounted. The kernel is configured to use ext4 for ext2/ext3.

What could I do wrong, how would you get the filesystem to boot?

My last error was:
List of all partitions:
0800 4013856 sda driver: sd
0801 64228 sda1 1d702457-01
0810 2000376 sdb driver: sd
0811 2000344 sdb1 0f93c873-01

No filesystem could mount root, tried: ext3 ext2 ext4 vfat ...
Kernel panic - not syncing: VFS: unable to mount root fs on unknown-block(8,1)

I don't know what to do with this error.

Please help me, thanks!

I can't give you exact solutions as I have no time to trouble shoot your kernel but

1) assuming bootable disk image means an iso image for an optical disk
you need to specify what bootloader you are using
---some people use syslinux other use other things
---some people use http://unetbootin.sourceforge.net/

b) if you mean an bootable drive image....same deal altho the actual commands may differ

2) the kernel must have INBUILT support for each partition its trying to boot
---so automatically fails if a module
hint....recompile to add full ext2/3/4 as in built pls

3) I hope this is just poor wording
kernel must be outside rootfs (initrd)

good luck

Thank you for your answer.

1) I mean a bootable drive image. Our customers have industrial pcs and those boot systems on compact flash cards. They can get new images with a bootable partition on it from us when there are updates.

2) I build the system with "buildroot" and marked the ext4 option and the option to use ext4 for ext2 and ext3 in the kernel configuration.

3) I get a filesystem for example in a tar-File. There I can browse through the folders /boot , /dev and so on .....
There exists a file bzImage in /boot which is actually the kernel image.
I am currently using grub as bootloader. For installing grub you have to set the path to the kernel image in the root filesystem. I set /boot/bzImage.

I thought that you don't need to have initrd?

So actually you just need the filesystem, the partition table and a way to get this on the flash, right? In that case just install everything on a system. Then make a backup of the mbr and the filesystem. Then create some livecd which all gets this to the flash card. Maybe check out clonezilla live cd.

Okay so the kernel now is able to use the ext family of filesystem. More important is what the filesystem of your root filesystem is. That is definitely to be going into the kernel as well.

grub needs a "root" device to know where it is to look out for the kernel and/or initrd. This is set with set root='(/dev/sd#,partitionnumber). Technicaly this is not needed but if you would give any path info to the kernel option you would have to state the root device as well.
So to actually boot a kernel grub only needs one line: linux (device)/boot/bzImage root=/dev/sd#
the root= here is the actuall path of the device that holds your root filesystem. It could also be given using UUID syntax.


Actually you don't need an initrd as long as the kernel has all the features compiled into it that are needed to get the root file system up. That is y in kernel configuration and not m like in module.