> 
>  I tried to update 1.2C to 1.2G;
> dd if=tk50-file2-12G  of=/dev/ra0d
>  then I just  copied boot and netbsd from ra0d to my root partition;
> and now it cannot start at all.
> After howto=...
> it falls in HLT instruction...
> What's hell?
> Please, help me, if anybody already passed through this trouble....
> 
You also need new bootblocks. If you have your new bootblocks in
/usr/mdec then just do: disklabel -B ra0 or whichever your root disk is.

-- ragge