[U-Boot-Users] USB booting...

Neil Bryan nbryan at embebidos.com
Wed Jul 6 17:33:48 CEST 2005

I am attempting to boot Linux on a target platform using a
USB mass storage device (flash disk) to hold the kernel and the 
root filesystem.

I thought it may be a good idea to replicate the same steps 
used when booting from a tftp server, i.e. I copy the root 
filesystem (using an initrd image) to an address in RAM, then 
copy the kernel to a different address in RAM.  Finally bootm with 
the start address of the kernel. Bootargs will be set during this 

So I created two partitions on the USB flash disk, partion 1 holds 
the kernel image and partition 2 holds the initrd image.  

The partition table looks like this:

Disk /dev/sdb: 32 MB, 32768000 bytes
2 heads, 32 sectors/track, 1000 cylinders
Units = cylinders of 64 * 512 = 32768 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sdb1             1       154      4912   83  Linux
/dev/sdb2           155       308      4928   83  Linux

My file sizes are:

initrd: 1203800 bytes.
uImage: 2285056 bytes.

The command I want to use to copy the initrd is:

usb read 20800000 x y.

Where 20800000 is the address for the initrd to be copied to, 
x will be the block-offest to the start of partition 2 and y will be 
the size in blocks of the initrd image.

Now I need to calculate the block-size based on cylinders, heads,
units etc.

My questions are, am I making this too complex, is there an easier way
to achieve the same result of booting using a USB flash disk with 
seperate kernel/initrd images?

Appologies for the long-winded pre-amble, but I don't know how to ask a
question like this without describing the problem.

Thanks for any insight,


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