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Subject: Re: Block device emulation on top of ubi volumes with read/write
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To: Daniel Ehrenberg <dehrenberg@google.com>,
 Charles Godson <cestgodson@gmail.com>
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From: Richard Weinberger <richard@nod.at>
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Date: Thu, 21 Jan 2016 01:12:36 +0100
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Am 21.01.2016 um 00:54 schrieb Daniel Ehrenberg:
> On Wed, Jan 20, 2016 at 3:30 PM, Charles Godson <cestgodson@gmail.com> wrote:
>> Thanks for quick reply. I replaced YAFFS2 root file system with SQUASHFS on
>> top of UBI [1], and so far it works like a charm. I am currently using UBIFS
>> on "user" partitions. Mostly, I needed quota on them, and there was nothing
>> in the works about a year ago. I was exploring different avenues: add quota
>> support to UBIFS or use [2]. However, I saw that UBIFS quota support is
>> introduced somewhere in July [3].
>>
>> After your explanations and suggestions above, I think ext4 is not really an
>> option for me. Since quota support for UBIFS is already in the works, the
>> choice is fairly clear :) .
>>
>> Thanks for your help on this.
>>
>> [1] http://lists.infradead.org/pipermail/linux-mtd/2014-February/052261.html
>> [2] https://lwn.net/Articles/525957/
>> [3] https://lwn.net/Articles/651925/
>>
>> Best regards,
>> Charles
>>
> I was also looking into using squashfs on top of ubiblock, hoping to
> write to overwrite a particular entire UBI partition with read-write
> ubiblock support. I ended up using separate MTD partitions each
> squashfs volume, with an UBI instance on each one, which could then be
> updated using the ubi formatting tools, rather than writing through
> ubiblock. Maybe UBIFS would be a better design, in retrospect.

What is wrong with having a single MTD parition and multiple UBI volumes?
You can use ubiupdatevol to update your squahsfs.

Thanks,
//richard