The linux kernel can be updated while the system is still operational. For this the kernel image is copied to the target system using SCP (Linux scp-command or WinSCP for Windows), for example to “/tmp/uImage”. Afterwards the following command has to be executed on the target as user root:
dd if=/tmp/uImage of=/dev/mmcblk0p2 ibs=512 seek=256 conv=sync,notrunc
The target system can be accessed via the serial interface (console) or SSH (Linux ssh-command or Putty for Linux and Windows).
Using a linux workstation this can be done in just one step (supposing the IP addresse of the targets is 172.16.135.170, the kernel image uImage is located in the current directory):
ssh root@172.16.135.170 dd of=/dev/mmcblk0p2 ibs=512 seek=256 conv=sync,notrunc <uImage
At the next restart the system will boot the new kernel.