[Buildroot] [PATCH] Makefile: Fix overlay overwriting everything

[Maxime Hadjinlian]

Hi Arnout, all

On Wed, Feb 10, 2016 at 9:09 PM, Arnout Vandecappelle <arnout at mind.be> wrote:
> On 10-02-16 16:58, Maxime Hadjinlian wrote:
>> After bumping from a 2 years old Buildroot installation, I got the
>> following messages from the kernel at boot:
>>
>> Failed to execute /init (error -2)
>>
>> It appears that the overlay mechanisms was causing my issues.
>>
>> Description:
>> The overlay mechanisms works by rsync'ing files from a folder specified
>> by the user into target.
>> Since c5bd8af65e50a51735eb112fed9cbe6337f14e06, /bin, /sbin and /lib are
>> symlinked into /usr.
>>
>> Problem:
>> If you have an overlay that contains the directory /bin, /sbin or /lib, rsync
>> will erase the symlink and create a directory in its place.
>> The directory, say .../target/lib, would *only* contains the overlay's content.
>> Obviously, this causes a lot of troubles, starting with the kernel
>> failing to start init (because of missing shared libraries).
>>
>> Solution:
>> Telling rsync to treat symlinked dir on the receiver side as directory
>> allow users to be blissfully ignorant of that problem.
>
>  I'm not so sure of this one... It makes it impossible to override the symlinks
> in the skeleton in the overlay. Say, you want to populate /var/spool with some
> directories so it becomes useable.
Just a precision: it's not all the symlinks only the symlinks that
points to a directory, like /var/spool
>
>  That said, it's probably better in that case to override the skeleton directly,
> so that package installation can pick up the new directory.
>
>  Still, you _are_ breaking a valid use case with this patch.
Another way to deal with this, is to test if in the overlay, there's a
a folder that is a link is the default skeleton and in that case,
treat it differently.
In the spur of the moment it seems too complicated. But maybe it's the
right solution after all.
>
>  What do the others think?
>
>  Regards,
>  Arnout
>
>>
>> Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian at gmail.com>
>> ---
>>  Makefile | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Makefile b/Makefile
>> index 71735b5..2f33ddf 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -655,7 +655,7 @@ endif
>>
>>       @$(foreach d, $(call qstrip,$(BR2_ROOTFS_OVERLAY)), \
>>               $(call MESSAGE,"Copying overlay $(d)"); \
>> -             rsync -a --ignore-times $(RSYNC_VCS_EXCLUSIONS) \
>> +             rsync -a --keep-dirlinks --ignore-times $(RSYNC_VCS_EXCLUSIONS) \
>>                       --chmod=u=rwX,go=rX --exclude .empty --exclude '*~' \
>>                       $(d)/ $(TARGET_DIR)$(sep))
>>
>>
>
>
> --
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
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