[Buildroot] Read only rootfs with writable (aufs) overlay

[Buildroot] Read only rootfs with writable (aufs) overlay

[Alex Hildebrand]

Hi there,
Does anyone of you have experience with a rootfs with a writable (aufs) overlay?
I managed to compile aufs and mount a folder combining the read only rootfs with a read write data overlay. How to switch the rootfs to this mount point? Tried to move the mount point to this folder in the inittab, but this fails with "Too many levels of symbolic links"
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[Buildroot] Read only rootfs with writable (aufs) overlay

[Bryce Ferguson]

Hi Alex,


On Mon, Feb 19, 2018 at 1:32 PM, Alex Hildebrand
<alexander.hildebrand@googlemail.com> wrote:
> Hi there,
>
> Does anyone of you have experience with a rootfs with a writable (aufs)
> overlay?
>
> I managed to compile aufs and mount a folder combining the read only rootfs
> with a read write data overlay. How to switch the rootfs to this mount
> point? Tried to move the mount point to this folder in the inittab, but this
> fails with "Too many levels of symbolic links"
>

I'm not sure I understand the question fully. Are you saying you want
the entire filesystem to be in the aufs? Why not use a RW filesystem
instead?

> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
>



-- 


Bryce Ferguson
Software Engineer
Airborne Information Solutions \ RC Linux Platform

400 Collins Rd NE Cedar Rapids, Iowa 52498

Bryce.Ferguson at rockwellcollins.com

[Buildroot] Read only rootfs with writable (aufs) overlay

[Peter Korsgaard]

>>>>> "Alex" == Alex Hildebrand <alexander.hildebrand@googlemail.com> writes:

 > Hi there,
 > Does anyone of you have experience with a rootfs with a writable (aufs) overlay?
 > I managed to compile aufs and mount a folder combining the read only
 > rootfs with a read write data overlay. How to switch the rootfs to
 > this mount point? Tried to move the mount point to this folder in the
 > inittab, but this fails with "Too many levels of symbolic links"

I don't have any specific experience with aufs (any specific reasons to
not use the in-kernel overlayfs instead), but you would normally need to
setup the overlay in an initramfs and then switch_root to it before
executing init.

-- 
Bye, Peter Korsgaard

[Buildroot] Read only rootfs with writable (aufs) overlay

[Alex Hildebrand]

So switch_root does not work when used without an initramfs? Tried it directly from my read only rootfs but it does not change the root...
Is this the same with in-kernel overlayfs?
-------- Urspr?ngliche Nachricht --------Von: Peter Korsgaard <peter@korsgaard.com> Datum: 19.02.18  22:46  (GMT+01:00) An: Alex Hildebrand <alexander.hildebrand@googlemail.com> Cc: buildroot at buildroot.org Betreff: Re: Read only rootfs with writable (aufs) overlay 
>>>>> "Alex" == Alex Hildebrand <alexander.hildebrand@googlemail.com> writes:

 > Hi there,
 > Does anyone of you have experience with a rootfs with a writable (aufs) overlay?
 > I managed to compile aufs and mount a folder combining the read only
 > rootfs with a read write data overlay. How to switch the rootfs to
 > this mount point? Tried to move the mount point to this folder in the
 > inittab, but this fails with "Too many levels of symbolic links"

I don't have any specific experience with aufs (any specific reasons to
not use the in-kernel overlayfs instead), but you would normally need to
setup the overlay in an initramfs and then switch_root to it before
executing init.

-- 
Bye, Peter Korsgaard
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[Buildroot] Read only rootfs with writable (aufs) overlay

[Peter Korsgaard]

>>>>> "Alex" == Alex Hildebrand <alexander.hildebrand@googlemail.com> writes:

 > So switch_root does not work when used without an initramfs?

Correct. switch_root is specific to initramfs. See the description at
the bottom of switch_root.c:

https://git.buildroot.net/busybox/tree/util-linux/switch_root.c


 > Tried it directly from my read only rootfs but it does not change the
 > root...  Is this the same with in-kernel overlayfs?

Yes, this is independent of the overlay fs implementation. If you only
want to add the overlay to a subset of the tree (E.G /etc), then you can
do it from your rootfs, but not when you want to replace /.

-- 
Bye, Peter Korsgaard