No AUFS in kernel - Can we do the same?

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efgee
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No AUFS in kernel - Can we do the same?

Postby efgee » 29 Apr 2014, 17:45

Read the announcement of a new Zenwalk version on Distrowatch and what got my attention was this:
This is the first Zenwalk Live version that is NOT using an Aufs-enabled kernel but instead running Unionfs in userspace via FUSE on an unmodified Slackware generic kernel.

If we (well actually sim :mrgreen: ) could implement the same, then we would not need to compile our own kernel but could use an arch generic one.
Maybe there are other reasons why we need our own kernel... if not, is this a viable solution in order to use generic kernels?
DIscussion welcome :)

Scooby
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Re: No AUFS in kernel - Can we do the same?

Postby Scooby » 29 Apr 2014, 20:22

And the benefits would be? To change kernel easy? upgrade kernel?


from http://podgorny.cz/moin/UnionFsFuse wrote:Why choose this stuff

The filesystem has to be mounted after the roots are mounted when using the standard module. With unionfs-fuse, you can mount the roots later and their contents will appear seamlesly
You get caching which speeds things up a lot for free
You get nice stats (optional)
Advanced features like copy-on-write and more

Why NOT choose it

Compared to kernel-space solution we need lots of useless context switches which makes kernel-only solution clear speed-winner (well, actually I've made some tests and the hard-drives seem to be the bottleneck so the speed is fine, too)


You had to rewrite or discard linux live kit for something else. Also bear in mind unionfs-fuse is nothing new, first release 2006

For me I cannot see enough benefits and it seems kernel-only is a bit speedier no matter what author of fuse version says,
check google for verification.

Aspi
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Re: No AUFS in kernel - Can we do the same?

Postby Aspi » 03 May 2014, 18:57

I think it sounds appealing. One could then easily put in one's own kernel, be it linux-libre or linux-grsec. A generic kernel is in general, more general, so it has better compatibility.

If this means ditching LLK, then it's prolly not worth it. I'll look at the inner workings of alphaOS some time.

On a different side: LLK seems to suggest just using an aufs and squashfs kernel module, which sounds like the best solution. FUSE is slower. Is there something restricting this use?

Scooby
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Re: No AUFS in kernel - Can we do the same?

Postby Scooby » 06 May 2014, 19:10

Aspi wrote:Is there something restricting this use?

OK I now understood what you meant.

But what would be benfit of aufs as a module?

You could not unload it and use FUSE. Not when in use
You still would have to heavily modify boot scripts.

I really don't think it changes anything, does it?

But sure you could redo alphaOS using aufs as a module, yes

Aspi
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Re: No AUFS in kernel - Can we do the same?

Postby Aspi » 07 May 2014, 06:49

^easier to use with custom kernels, and the vanilla kernel of course. Which could mean fetching the binary kernel from arch could be possible. I bet Sim would like that :P
It's more modular. Imo, it's like using functions in code in contrast to doing it all in sequel. It's more modular.

Scooby
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Re: No AUFS in kernel - Can we do the same?

Postby Scooby » 07 May 2014, 17:21

from aufs sourceforge

Code: Select all

aufs3
Currently aufs3 supports these kernels.

linux-3.x-rcN     latest mainline
linux-3.14    stable
linux-3.13    stable
linux-3.12    longterm
linux-3.12.x    for v3.12.7 and later
linux-3.11    [EOL]
linux-3.10    longterm
linux-3.10.x    for v3.10.26 and later
linux-3.9    [EOL]


and this is true for kernel config CONFIG_AUFS_FS=y or CONFIG_AUFS_FS=m

You would not get around limitation on what kernel to use.

Aspi
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Re: No AUFS in kernel - Can we do the same?

Postby Aspi » 07 May 2014, 22:35

I see. It's all explained at their home page. Btw, there is a nice little PKGBUILD for linux-aufs_friendly, I reckon alphaOS uses this or something equivalent.

So, some info on union file systems:
Status of OverlayFS and Union Filesystems in General
Rarely Mentioned Pseudo-filesystems
OverlayFS File-System Proposed For Linux 3.10 Kernel
semi-old Ubuntu view of union file systems

Still, I think AUFS > OverlayFS, without having looked at it on any deeper level than ^
But as OverlayFS might get merged, perhaps it will be time to migrate. Brace ourselves.


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