View source for Kernelimage

As stated in [[Generated Images]], buildroot provides a dedicated kernel-image called uImage. As the bootloader can not read all filesystems by default, this has to be flashed into a separate partition of the NAND-Flash.


== Writing the image into flash ==

While booting via NFS, a new kernel can be flashed by first erasing the first NAND-partition and write the Image directly into that partition afterwards. This can be done by using the following commands:

  flash_eraseall /dev/mtdX
  dd if=/boot/uImage of=/dev/mtdblockX bs=131072

where mtdX and mtdblockX specify the flash partition in which the kernel resides. More information about the mtd devices may be available from the command "mtdinfo /dev/mtdX".

This would write the kernelimage found at ''/boot/uImage'' into the partition X. The parameter ''bs'' specifies the blocksize to use and should match the sector-size of the flash in use. It would work with other sizes, too, but would unnecessarily stress the device and take a larger amount of time.

On some devices the command flashcp is available which is a better alternative to dd. Use it as following:
  flashcp /boot/uImage /dev/mtdX

If your Kernel Version does not support the flash_eraseall Command, use
  flash_erase /dev/mtdX 0 0
instead. This should work on newer Versions.

== Booting the new image ==

With the default environment, the device will automatically boot the new kernel, the next time it is started. 
If the environment has changed, eg. for booting via [[Network File System (NFS)|NFS]], the following line can be used to boot the new kernel from flash once

  mtdparts default; nand read 0x70400000 nand0,0; bootm

To store this configration and making the kernel being loaded from flash by default, the following lines can be used:

  askenv bootcmd
  mtdparts default; nand read 0x70400000 nand0,0; bootm
  saveenv


[[Category:Filesystems]] [[Category:HowTo]]