Hi All

I realise this question is a little off the wall but I'm looking for a way to test a kernel without actually installing it.

The reason for this is that I want to make a modification to the existing kernal on my (debian) NAS. The bootloader and kernel are both stored in flash memory on the board but there is no way to write to this except through the opperating system itself (via SSH). The bootloader doesn't have hard disk support. So if I change the kernal and find that it no-longer boots then I'll have bricked my NAS.

I was hoping that there may be a way to get a linux install to act like an oversized bootloader and kick off a seperate kernal.

I realised this a rather odd requirement so any suggestions welcome.

Thanks

This is what the "kexec()" syscall is for -- there's userland support for this called "kexec-tools". But I never tried it myself. Good luck

Exact same thing I was thinking, but I too have never even thought of using it, let alone tried it. Here's a good writeup on it:
http://www.ibm.com/developerworks/li...y/l-kexec.html

Oh wow. The kexec sounds really cool. I need to check this out and try it out. BUT.





Im assuming it's only a short matter of time before x86_64 will be supported? :fingers crossed:

Good question indeed.. I didn't note how old was the article I linked above, but doing a google for "64 bit kexec" turns up a LOT of hits, particularly for "64bit kexec-tools package".

LOL... I'd say maybe a 64bit version it out by now. I haven't searched nor did I pay attention to the date.

Hmm, if it isn't supported right now, it could be due to hardware limitations. The following are just assumptions (didn't check that):
- Maybe kexec() on x86 switches the processor back to real mode before exec()ing the bootup code of the kernel
- Maybe there's no (easy) way to get back to real (or even protected) mode from long mode in x86_64 ...
edit: But it looks like this isn't really necessary (OR solved) by now

Here's a question that may be relevant, but I don't know the answer to: What architecture is the NAS?

I did notice kexec search results that referred to MIPS architecture.. So, what's the NAS running on?

Moved: This thread is more suitable in Linux-Kernel and has been moved accordingly to help your thread/question get the exposure it deserves.

You have to build the kexec support into the base (running) kernel - check our config. You may be up for more than one build ....

Sadly there are two problems with kexec in my case.
1: It's an ARM chip (Marvell Orion)
2: I dont *think* (havn't checked) that this support is in my current kernel. This creates a sort of catch 22.