bitbaking aufs

bitbaking aufs

[Vitus Jensen]

Hej!

I would like to use a layered filesystem in our ppc603e-based machine: the 
rootfs built from openembedded would be read-only, any customizations go 
to a writable filesystem and should the need occur to start fresh all I 
need is a mechanism to remove the contents of the writable filesystem.

In openembedded (2011.03) there is unionfs and aufs 
(http://aufs.sourceforge.net/), aufs is more actively developed so I would 
like to use that.  Unfortunately the recipe in oe uses aufs1 which does 
not support current kernels.  Could change that to aufs2.2 but 
aufs2 now has two seperated repos (patched kernel or source plus patches = 
"standalone") and I'm in doubt how to proceed.  Especially as aufs_cvs.bb 
contains some CONFIG_xxx voodo.

My intention is to use the "standalone" repo and "inherit module" from oe 
but how do I apply kernel patches in this case?  The kernel resides in 
${TMPDIR}/sysroots, do I patch that???  Or do I have to apply those 
patches during kernel build?  I could extract them from git and add them 
to the kernel recipe for my machine but this doesn't feel right,

I think, I need some advice how to best get aufs2.2 building.  And a good 
example for a "inherit module" recipe using sysroot kernel source might 
help.  Which should I use as example for aufs?

Best regards,
    Vitus

-- 
Vitus Jensen, Hannover, Germany, Universe (current)
pgp public key available from keyservers

Re: bitbaking aufs

[Thomas Zimmermann]

On Wednesday, August 24, 2011 00:11:39 Vitus Jensen wrote:
> Hej!
> 
> I would like to use a layered filesystem in our ppc603e-based machine: the
> rootfs built from openembedded would be read-only, any customizations go
> to a writable filesystem and should the need occur to start fresh all I
> need is a mechanism to remove the contents of the writable filesystem.
> 
> In openembedded (2011.03) there is unionfs and aufs
> (http://aufs.sourceforge.net/), aufs is more actively developed so I would
> like to use that.  Unfortunately the recipe in oe uses aufs1 which does
> not support current kernels.  Could change that to aufs2.2 but
> aufs2 now has two seperated repos (patched kernel or source plus patches =
> "standalone") and I'm in doubt how to proceed.  Especially as aufs_cvs.bb
> contains some CONFIG_xxx voodo.
> 
> My intention is to use the "standalone" repo and "inherit module" from oe
> but how do I apply kernel patches in this case?  The kernel resides in
> ${TMPDIR}/sysroots, do I patch that???  Or do I have to apply those
> patches during kernel build?  I could extract them from git and add them
> to the kernel recipe for my machine but this doesn't feel right,
> 
> I think, I need some advice how to best get aufs2.2 building.  And a good
> example for a "inherit module" recipe using sysroot kernel source might
> help.  Which should I use as example for aufs?
> 
> Best regards,
>     Vitus

You have to patch the kernel to export a lot of symbols for aufs2. So you have 
to rebuild the kernel anyway. And then i think it would be the easiest way if 
you integrate it into your kernel directly. Like described in the README 
section 3.1.

In my opinion a standalone aufs recipe is not possible, because the kernel 
needs to be patched and you have to use the specific branch for your kernel 
version.

Regards
Thomas

Re: bitbaking aufs

[Vitus Jensen]

On Wed, 24 Aug 2011 11:02:05 +0200 Thomas Zimmermann wrote:
> On Wednesday, August 24, 2011 00:11:39 Vitus Jensen wrote:
> > Hej!
> > 
> > I would like to use a layered filesystem in our ppc603e-based machine:
> > the rootfs built from openembedded would be read-only, any
> > customizations go to a writable filesystem and should the need
> > occur to start fresh all I
> > need is a mechanism to remove the contents of the writable filesystem.
> > 
> > In openembedded (2011.03) there is unionfs and aufs
> > (http://aufs.sourceforge.net/), aufs is more actively developed so
> > I would like to use that.  Unfortunately the recipe in oe uses
> > aufs1 which does
> > not support current kernels.  Could change that to aufs2.2 but
> > aufs2 now has two seperated repos (patched kernel or source plus
> > patches = "standalone") and I'm in doubt how to proceed.
> > Especially as aufs_cvs.bb contains some CONFIG_xxx voodo.
> > 
> > My intention is to use the "standalone" repo and "inherit module"
> > from oe
> > but how do I apply kernel patches in this case?  The kernel resides in
> > ${TMPDIR}/sysroots, do I patch that???  Or do I have to apply those
> > patches during kernel build?  I could extract them from git and add
> > them to the kernel recipe for my machine but this doesn't feel right,
...

> You have to patch the kernel to export a lot of symbols for aufs2.
> So you have  to rebuild the kernel anyway. And then i think it
> would be the easiest way if you integrate it into your kernel
> directly. Like described in the README section 3.1.
> 
> In my opinion a standalone aufs recipe is not possible, because the
> kernel needs to be patched and you have to use the specific branch
> for your kernel version.

In this case (and in the meantime I came to the same conclusion) it is easiest to use the already patched kernel tree from aufs.sourceforge, create a linux-aufs_2.6.36.bb and use that for my device.  Or have a second look to union-mount (http://valerieaurora.org/union/) and build a recipe for that tree.

Thank you for your viewpoints, they helped.
  Vitus

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Re: bitbaking aufs

[Vitus Jensen]

On Wed, 24 Aug 2011, Vitus Jensen wrote:

> On Wed, 24 Aug 2011 11:02:05 +0200 Thomas Zimmermann wrote:
>> On Wednesday, August 24, 2011 00:11:39 Vitus Jensen wrote:
>>>
>>> I would like to use a layered filesystem in our ppc603e-based machine:
>>> the rootfs built from openembedded would be read-only, any
>>> customizations go to a writable filesystem and should the need
>>> occur to start fresh all I
>>> need is a mechanism to remove the contents of the writable filesystem.
>>>
>>> In openembedded (2011.03) there is unionfs and aufs
>>> (http://aufs.sourceforge.net/), aufs is more actively developed so
>>> I would like to use that.
...

>> In my opinion a standalone aufs recipe is not possible, because the
>> kernel needs to be patched and you have to use the specific branch
>> for your kernel version.
>
> In this case (and in the meantime I came to the same conclusion) it is 
> easiest to use the already patched kernel tree from aufs.sourceforge, 
> create a linux-aufs_2.6.36.bb and use that for my device.  Or have a 
> second look to union-mount (http://valerieaurora.org/union/) and build a 
> recipe for that tree.

FYI:

Built a linux-unionmount 2.6.35 kernel recipe plus 
initramfs-module-unionmount and installed that.  I did encounter problems 
to mount the upper-half (filesystems ext2 and jffs2 weren't accepted) and 
when googling for help I found that the race for kernel tree acceptance is 
still open: it might be overlayfs and not union-mount.  Let's wait some 
years and see :-(

As I need a working solution now and aufs2 is actively developed 
(ready-to-be-made kernel trees up to 3.0.0) I will now create a 
linux-aufs2 bb.

Bye,
    Vitus

-- 
Vitus Jensen, Hannover, Germany, Universe (current)
pgp public key available from keyservers