[OE-core] Contents of non-rootfs partitions

[Kristian Amlie]

On 24/11/16 14:23, Ed Bartosh wrote:
> On Thu, Nov 24, 2016 at 08:38:46AM +0100, Kristian Amlie wrote:
>> On 24/11/16 07:15, Ulrich Ölmann wrote:
>>> Hi,
>>>
>>> On Wed, Nov 23, 2016 at 04:56:56PM +0100, Patrick Ohly wrote:
>>>> On Wed, 2016-11-23 at 15:22 +0200, Ed Bartosh wrote:
>>>>> On Wed, Nov 23, 2016 at 02:08:28PM +0100, Kristian Amlie wrote:
>>>>>> On 23/11/16 13:08, Ed Bartosh wrote:
>>>>>>> On Tue, Nov 22, 2016 at 12:54:52PM +0100, Kristian Amlie wrote:
>>>>>>> [...]
>>>>>>> This can be done by extending existing rootfs plugin. It should be able
>>>>>>> to do 2 things:
>>>>>>>
>>>>>>> - populate content of one rootfs directory to the partition. We can
>>>>>>>   extend syntax of --rootfs-dir parameter to specify optional directory path to use
>>>>>>>
>>>>>>> - exclude rootfs directories when populating partitions. I'd propose to
>>>>>>>   introduce --exclude-dirs wks parser option to handle this.
>>>>>>>
>>>>>>> Example of wks file with proposed new options:
>>>>>>> part /     --source rootfs --rootfs-dir=core-image-minimal       --ondisk sda --fstype=ext4 --label root --align 1024 --exclude-dirs data --exclude-dirs home
>>>>>>> part /data --source rootfs --rootfs-dir=core-image-minimal:/home --ondisk sda --fstype=ext4 --label data --align 1024
>>>>>>> part /home --source rootfs --rootfs-dir=core-image-minimal:/data --ondisk sda --fstype=ext4 --label data --align 1024
>>>>>>>
>>>>>>> Does this make sense?
>>>>>>
>>>>>> Looks good. The only thing I would question is that, in the interest of
>>>>>> reducing redundancy, maybe we should omit --exclude-dirs and have wic
>>>>>> figure this out by combining all the entries, since "--exclude-dirs
>>>>>> <dir>" and the corresponding "part <dir>" will almost always come in
>>>>>> pairs. Possibly we could mark the "/" partition with one single
>>>>>> --no-overlapping-dirs to force wic to make this consideration. Or do you
>>>>>> think that's too magical?
>>>>>>
>>>>> Tt's quite implicit from my point of view. However, if people like it we
>>>>> can implement it this way.
>>>>
>>>> I prefer the explicit --exclude-dirs. It's less surprising and perhaps
>>>> there are usages for having the same content in different partitions
>>>> (redundancy, factory reset, etc.).
>>>>
>>>> Excluding only the directory content but not the actual directory is
>>>> indeed a good point. I'm a bit undecided. When excluding only the
>>>> directory content, there's no way of building a rootfs without that
>>>> mount point, if that's desired. OTOH, when excluding also the directory,
>>>> the data would have to be staged under a different path in the rootfs
>>>> and the mount point would have to be a separate, empty directory.
>>>>
>>>> I'm leaning towards excluding the directory content and keeping the
>>>> directory.
>>>
>>> what about having both possibilities by leaning against the syntax that rsync
>>> uses to specify if a whole source directory or only it's contents shall be
>>> synced to some destination site (see [1])?
>>>
>>> In analogy to this to exclude only the contents of the directory named 'data'
>>> you would use
>>>
>>>   --exclude-dirs data/
>>>
>>> but to additionally exclude the dir itself as well it would read
>>>
>>>   --exclude-dirs data
>>
>> This is creative, but ultimately too unintuitive IMHO. Rsync is the only
>> tool which uses this syntax AFAIK, and it's a constant source of
>> confusion, especially when mixed with cp or similar commands.
>>
> 
> Would this way be less intuitive?
> --exclude-path data/*
> --exclude-path data
> 
> We can go even further with it allowing any level of directories:
> --exclude-path data/tmp/*
> --exclude-path data/db/tmp
> ...

I agree, this is pretty unambiguous and easy to understand.

But this raises the question: Should we go all the way and support
wildcards? Which might make it a bit complicated. Maybe support only
pure '*' for now?

-- 
Kristian