[Buildroot] Building multi-part rootfs images

Arnout Vandecappelle arnout at mind.be
Mon Apr 10 22:09:35 UTC 2017



On 11-04-17 00:05, Christian Stewart wrote:
> Hi Arnout,
> 
> On Mon, Apr 10, 2017 at 5:57 PM, Arnout Vandecappelle <arnout at mind.be> wrote:
>>  Loop-mount? It should be a normal mount, no?
> 
> I said "loop mount" (forgive me if the terminology is wrong) because
> I'm still operating under a "binary blob" system where I'm not
> mounting anything r/w against the disk, so I would likely mount a loop
> filesystem (-o loop) to /lib/modules.

 Loop mount indeed means -o loop, but that's used to mount a normal file where a
block device is expected. What you want is to mount a different partition (or
UBI volume, or NFS export) on /lib/modules. At least, that's what I think you mean.

> 
>> - mounting specific subdirs. Quite easy to implement:
> 
> This seems like the most straightforward approach, especially since
> the kernel shouldn't need any modules until way later in the boot
> anyway. I can add a systemd blocking early step that does the mount.

 systemd already has that for anything specified in /etc/fstab. It's not
blocking, though.


 Regards,
 Arnout

> 
>>   - in post-build, move away the subdirs you want to mount from somewhere else
>> to a temporary directory. E.g., mv $TARGET_DIR/lib/modules $BINARIES_DIR/modules;
>>   - add a genimage.cfg that makes some filesystem out of $BINARIES_DIR/modules;
>> the same genimage.cfg can also put the rootfs.cpio and zImage somewhere where
>> the bootloader can find it;
>>   - call genimage.sh as a post-build script;
>>   - in your rootfs overlay, add /etc/fstab that mounts the filesystem.
> 
> This makes sense. I'll prototype this and report back with results.
> 
> Source code is available at http://github.com/paralin/skiffos
> 
> Thanks again!
> Christian
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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