[OT] initramfs, max size?

[Thomas Kaiser]

Bruce Marshall wrote:
> On Wednesday 05 December 2007, Thomas Kaiser wrote:
>> I am plying with initramfs and got some problem to load big initramfs
>> images. My goal is to run my little ubuntu, about 150~ MB, totally in ram.
>> Grub does not load such a big initrd :-) . I tried  a 7MB image which
>> worked OK but the next one was about 14M and grub refused to load :-)
>>
>> Any help or pointers to which ML I should write.
> 
> 1. The kernel has to set aside room for the initramfs so you are limited by 
> what was specified for the kernel.

As far as I read, initramfs has no such limitation like th older initrd thing.

> 
> 2.  The modules in initramfs are only used at boot time so that certain 
> functions are available early on in the boot process.   After the boot is 
> finished, normal module loading occurs and the modules in initramfs are no 
> longer used.

Actually, there are not only modules in the initramfs image. It's a whole 
environment with a shell and boot scripts and so on. On a "normal" system the 
initramfs image is used to set up the PC's hardware before the real root 
partition gets mounted, but this depends what is programmed in the initramfs 
image. You don't have to mount a root partition after the scripts in initramfs 
are executed. See https://linuxlink.timesys.com/docs/initramfs.
> 
> I think you'd better read up on the boot process.

I did ;-) and you?

> 
> A better method would be to compile your own kernel and only include those 
> modules needed by your system, and build them right into the kernel.  No 
> initramfs would be needed and you could pare the kernel down a bit.
> 

That's the old fashioned way. Initramfs was introduced to avoid this ;-)

Looks like I have to dig into grub.

Thanks anyway.

Thomas


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