initrd support.

initrd support.

[moreau francis]

Hi,

I'm going to use initrd to mount my root fs, but I was
wondering what its status...
I have noticed in boot directory addinitrd program
that seems to add an initrd image right after the
kernel.
But there's also a section in kernel/vmlinux.lds.S
called
.initrd that includes initrd image during kernel 
compilation.

Why are there two different ways of using initrd ?
Which one I should use ?

Thanks for your answers.

Francis.


	

	
		
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Re: initrd support.

[Thiemo Seufer]

moreau francis wrote:
> Hi,
> 
> I'm going to use initrd to mount my root fs, but I was
> wondering what its status...
> I have noticed in boot directory addinitrd program
> that seems to add an initrd image right after the
> kernel.
> But there's also a section in kernel/vmlinux.lds.S
> called
> .initrd that includes initrd image during kernel 
> compilation.
> 
> Why are there two different ways of using initrd ?

Actually, there are three:
- the generic initramfs method for compiled in initrds
- the addinitrd method to attach a initrd to a precompiled kernel
  image (which is old, and essentially unmaintained)
- the rd_start/rd_size method, which allows a bootloader to load both
  kernel and initrd images into memory and then tells the kernel via
  the rd_start/rd_size parameters where the initrd is located

> Which one I should use ?

Depends on your machine/bootloader and how much flexibility you want.


Thiemo

Re: initrd support.

[moreau francis]

 --- Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
a écrit : 
> Actually, there are three:
> - the generic initramfs method for compiled in
> initrds
what's the difference with the rd_start/rd_size method
?

> - the addinitrd method to attach a initrd to a
> precompiled kernel
>   image (which is old, and essentially unmaintained)
why is it still in kernel's tree ? Is it going to be
removed ?

> - the rd_start/rd_size method, which allows a
> bootloader to load both
>   kernel and initrd images into memory and then
> tells the kernel via
>   the rd_start/rd_size parameters where the initrd
> is located
Why do I need to provide rd_start/ rd_size setup
parameters ? It's already provided by vmlinux.lds.S.

thanks,

Francis.



	

	
		
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Re: initrd support.

[Kumba]

Thiemo Seufer wrote:
> 
> Actually, there are three:
> - the generic initramfs method for compiled in initrds

Is there any docs for this floating around outside of the blurb on the LMO wiki?

Doing a few tests with this, I was unable to get a kernel to see the ramdisk. 
  Despite there being an initramfs built into the kernel, there were no 
"RAMDISK: Compressed ramdisk found at block 0" messages, or no "checking if 
image is initramfs...it isn't (no cpio magic); looks like an initrd" messages 
that I've commonly seen with built-in ramdisks.

I figure in the end, either the problem is PEBKAC, invalid kernel command line 
params (root=/dev/ram0?), or broken code.


--Kumba

-- 
"Such is oft the course of deeds that move the wheels of the world: small 
hands do them because they must, while the eyes of the great are elsewhere." 
--Elrond