[U-Boot] Rescue /alternative boot

[Arno Steffen]

Dear Albert,

2010/6/9 Albert ARIBAUD <albert.aribaud at free.fr>:
> If the user is able to do something stupid then you should avoid it, e.g.
> not give the user the ability to alter the u-boot environment by making it

In fact, the normal user doesn't have access to change it. But even I
can make faults.

> You should consider accessibility to the bootloader prompt as a critical
> requirement before considering resiliency -- actually, access to U-boot is a
> last-resort, but good, response to the resiliency requirement.

I am not free to change this anymore. So I have to find another way via network.

> Why can you not trust the u-boot environment? Maybe hardening the system
> against user-induced environment changes would help avoid the condition in
> the first place.

The system must be ready for updates - and they might go wrong, even by a typo.

>> - howto handle boot/kernel parameters? I only know the way via
>> environment variables
>
> As Wolfgang pointed out, read the manual: passing parameters does not depend
> on how you got the image in the first place, and works the same whether you
> use TFTP, flash or hard disks.

In manual I just can see how to set commandline parameters. Everything
( I understand until now) is controled via environment.
I have to put some code (before the environment is read) into uboot
source to force a tftpboot with in-compiled parameters. And I don't
have a clue howto and where to do this.
It is not enough to set some default environment, as this becomes
active only if CRC is failed. This will not help against a typo in the
setting.

Best regards
Arno