[Buildroot] [PATCH 1/5] Makefile: add media image generation

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, Vivien, All,

On 2015-03-19 09:27 +0100, Thomas Petazzoni spake thusly:
> On Thu, 19 Mar 2015 01:04:45 +0100, Yann E. MORIN wrote:
> > I've had a quick look at the examples you provide in later patches,
> > especially the RPi ones. You laways only have a single rootfs partition,
> > and there is no setup where you'd have (Rpi for example):
> > 
> >     /dev/mmcblk0p1  -->  fat       -->  -
> >     /dev/mmcblk0p2  -->  squashfs  -->  /
> >     /dev/mmcblk0p3  -->  ext4      -->  /usr/
> 
> Well, the examples are "defconfig" style examples, so in the spirit of
> Buildroot, they should implement the simplest case possible. It's then
> up to the user to further refine the configuration to adapt the
> filesystem layout to his needs.

Sorry, I might not have been clear: I think the defconfig are indeed OK.

However, what I wonder about, is that all those defconfigs rely on the
image already generated by Buildroot, and I fail to see how one would
write a mutli-partition genimage config file.

Furthermore, I've read the genimage docs (a mere README, far from being
complete), and it does not look obvious to me.

Also, rather than letting Buildroot build the filesystem images and then
aggregate that with genimage, it would be meuch more interesting (IMHO)
to provide an example that lets genimage do the filesystem. That would
be a good example on how to do it.

Also, in the case of multiple partitions, I wonder how /etc/fstab is
updated (since the current examples only use a pre-generated filesystem
image, they can't update fstab).

It might even be interesting to have an example (e.g. in the manual or
somewhere else...) with a more complex setup, like a multi-partition
setup where parts are inherited from Buildroot (the rootfs) and others
are generated by genimage, or whatever seemingly complex setup we can
come up with...

Regards,
Yann E. MORIN.

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