Re: [Buildroot] [PATCH 3/3] fs/dracut: new fs type

Le 18/12/2021 à 14:22, Yann E. MORIN a écrit :

Thierry, All,

Hi Yann,
Nice to hear from you again

On 2021-12-17 22:50 +0100, Thierry Bultel spake thusly:

quoted

Good idea. But dracut generates a gzipped cpio image.

That the cpio is gzipped is unfortuante, because the kernel will again
compress it as part of its own compression (whem it is used as an
initramfs, IIRC).

Yes, it is not aimed to be used like that.

Clearly, the origin of dracut is the desktop world (where the initrd is 
separated)

But I really found it convenient (as I say in the commit description) 
for the embedded
world, typically to build a recovery system (this is my use case)
In addition to the dracut features you mention in your other mail, there 
are also
the handling of dependencies to firmwares (provided that the kernel 
modules declare it
by the MODULE_FIRMWARE macro, and that is not the case of all of them, I
encountered some staging drivers that do not)
and the respect of symlinks.
The concept of dracut modules is nice, too.

quoted

Maybe, instead, the
"cpio" and "dracut" options (exclusives) could be but in a "Initial RAM
filesystem" menu.

We already have such a filesystem:
     fs/initramfs/
         "initial RAM filesystem linked into linux kernel"

And this one is tricky, because it hooks into linux/linux.mk with manual
and custom dependencies (see linux/linux.mk@571). I am not 100% happy on
how this is done, but we can't really have better...

So, I think that having dracut be an option of cpio is the easiest way
to go...

Thanks Yann, I agree, and I am about to send a patch set that does the 
trick like that.
Regards,
Thierry

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