How to load initramfs only on-demand?

[Woody Wu]

m

On Sunday, March 13, 2016, Woody Wu <narkewoody at gmail.com> wrote:

>
>
> On Sunday, March 13, 2016, Greg KH <greg at kroah.com
> <javascript:_e(%7B%7D,'cvml','greg at kroah.com');>> wrote:
>
>> On Sat, Mar 12, 2016 at 04:29:08PM +0800, Woody Wu wrote:
>> > My question is, is there such a kernel parameter to do the job?
>> Probably there
>> > is a non-parameter solution like passing the initramfs address in a
>> register
>> > when a boot loader transfer control to the kernel, but this is not an
>> option to
>> > me since my boot loader (u-boot) does not support doing this. Thanks.
>>
>> You have the source to your bootloader, I suggest you fix that up to
>> support this if you want it, not much the kernel can do on it's own
>> here, sorry.
>>
>>
> But the kernel document says,
>
> External initramfs images:
> --------------------------
>
> If the kernel has initrd support enabled, an external cpio.gz archive can
> also
> be passed into a 2.6 kernel in place of an initrd.  In this case, the
> kernel
> will autodetect the type (initramfs, not initrd) and extract the external
> cpio
> archive into rootfs before trying to run /init.
>
> This has the memory efficiency advantages of initramfs (no ramdisk block
> device) but the separate packaging of initrd (which is nice if you have
> non-GPL code you'd like to run from initramfs, without conflating it with
> the GPL licensed Linux kernel binary).
>
> It can also be used to supplement the kernel's built-in initramfs image.
> The
> files in the external archive will overwrite any conflicting files in
> the built-in initramfs archive.  Some distributors also prefer to customize
> a single kernel image with task-specific initramfs images, without
> recompiling.
>
> So I am thinking, can I from my bootloader load a cpio.gz into ram and
> start kernel with a command line "initrd=0x30000000"? Wii this work? And,
> in this case should I also pass kernel with someilike "roo=/dev/ram"?
> Thanks.
>
> -woody
>
>
> I found the initrd=address works! No root= need to be passed. Only let
u-boot load a cpio.uboot image into physical memory and set the correct
kernel command line, my problem solved. :-)



-- 
Life is the only flaw in an otherwise perfect nonexistence
    -- Schopenhauer

woody
public key at http://subkeys.pgp.net:11371 (narkewoody at gmail.com)
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