Re: [PATCH 1/1] linux-yocto 4.4: enable overlayfs by default

[Robert Yang <liezhi.yang@windriver.com>]

On 04/05/2016 10:31 AM, Bruce Ashfield wrote:
>
>
> On Mon, Apr 4, 2016 at 9:53 PM, Robert Yang <liezhi.yang@windriver.com
> <mailto:liezhi.yang@windriver.com>> wrote:
>
>
>     Hi Bruce,
>
>     How many union fs on Linux, please? AFAIK:
>     * unionfs: not supported by kernel any more.
>     * aufs
>     * overlayfs
>
>     If aufs and overlayfs are conflicted, how about:
>
>     KERNEL_UNION_FS ?= "features/overlayfs/overlayfs.scc"
>
>     KERNEL_EXTRA_FEATURES ?= "[snip] ${KERNEL_UNION_FS}"
>
>     I think that we really need a way to make iso/hddimg work by default
>     to enhance the OOBE.
>
>
> That sort of mechanism can work, but not if it is enabled by default. out of box
> experience
> is one thing, but there are plenty of boot and image types that don't need a
> unionfs, and
> we can't force these as =y for those image types.
>
> If we make a modular config, and a built-in config, we could pick the modular
> config by
> default, and then have the package list for the images that need them, rdepend
> on the
> appropriate modules.

Sounds good, so how about:

1) Update kernel to make overlayfs as module rather than builtin
2) let core-image-minimal-initramfs RDEPENEDS on the module.

// Robert

>
> Bruce
>
>
>     // Robert
>
>     On 04/04/2016 07:56 AM, Bruce Ashfield wrote:
>
>
>
>         On Sun, Apr 3, 2016 at 5:46 PM, Richard Purdie
>         <richard.purdie@linuxfoundation.org
>         <mailto:richard.purdie@linuxfoundation.org>
>         <mailto:richard.purdie@linuxfoundation.org
>         <mailto:richard.purdie@linuxfoundation.org>>>
>         wrote:
>
>              On Sun, 2016-04-03 at 06:11 -0400, Bruce Ashfield wrote:
>              >
>              >
>              > On Sun, Apr 3, 2016 at 5:58 AM, Robert Yang <
>              >liezhi.yang@windriver.com <mailto:liezhi.yang@windriver.com>
>         <mailto:liezhi.yang@windriver.com <mailto:liezhi.yang@windriver.com>>>
>         wrote:
>              > > So that iso can work well, otherwise the iso is readonly and there
>              > > would
>              > > be errors. The other way is aufs, but overlayfs is more pupolar and
>              > > had
>              > > been merged by kernel mainline, we need make iso work well by
>              > > default.
>              > Nope. As I mentioned before, this can't be a always on default. It
>              > will conflict
>              > with other unionFS use cases.
>              >
>              > If you want overlayfs enabled, it needs to be triggered from a
>              > specific image
>              > or distro feature.
>
>              We can't change the kernel config from an image so it would have to be
>              a distro setting. Is there a problem with enabling both as modules btw?
>              I assume they can coexist?
>
>
>         I've always found it limiting that we can't trigger kernel features based on
>         what an image'
>         type actually needs, but I understand why/how it works like this.
>
>         If it can't be triggered by an image setting, then just keeping a layer
>         that is
>         added
>         to the build, that has a bbappend with the appropriate KERNEL_FEATURES would
>         also work, and is the approach that I've also taken.
>
>         Not that the existing configs are great in this respect (they need a lot of
>         streamlining),
>         but building modules 'just in case' eventually leads to allmodconfig :)
>
>         I'd imagine they could co-exist, but it isn't something I've tried.
>
>         Bruce
>
>
>              Cheers,
>
>              Richard
>
>
>
>
>         --
>         "Thou shalt not follow the NULL pointer, for chaos and madness await
>         thee at its
>         end"
>
>
>
>
> --
> "Thou shalt not follow the NULL pointer, for chaos and madness await thee at its
> end"