linux-ext4 - Re: flashing large eMMC partitions with ext4

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Message-ID: <CAOQ4uxgKzpCp_xnr9Y+Fp3+N4GwTacGQYupGY_o+SFDZYjgiGQ@mail.gmail.com>
Date:	Tue, 2 Aug 2011 20:52:56 +0300
From:	Amir Goldstein <amir73il@...il.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Round Robinjp <roundrobinjp@...oo.co.jp>,
	Andreas Dilger <aedilger@...il.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: flashing large eMMC partitions with ext4

On Tue, Aug 2, 2011 at 7:57 PM, Ted Ts'o <tytso@....edu> wrote:
> On Wed, Aug 03, 2011 at 01:07:08AM +0900, Round Robinjp wrote:
>> So that means I have thrown away some important part of
>> the filesystem when I did truncate -s 1G, isn't it?
>> Will things go wrong if I flash this 1G image to my eMMC
>> partition (without using Yongqiang's new 64bit resize patches)?
>> I need to understand whether Yongqiang's patch is absolutely
>> necessary for this purpose or just a good thing to have.
>
> This is one of the reasons why I originally suggested using zero_free
> and make_sparse to write the file system image.  It's a much, much,
> MUCH simpler way of handling things, and it doesn't require resizing
> the file system image, using truncate (and making sure you truncate to
> the right size, etc.).
>
> With the method Amir talked about, it matters whether or not the file
> system is mounted when you use resize2fs, whether you have the latest
> resize patches, etc., etc.
>

I think it is fair to say that with if there are no constrains on the methods
used throughout the process, the zero_free + make_sparse is MUCH simpler.

However, my method is targeting an a-symmetric environment, where the
person or organization  responsible for generating the stock image
have unlimited
resources and knowledge, while the person or organization  responsible for
burning that image to hundreds of devices are less capable or bound to using old
legacy systems, who just know how to burn an image of size N.

Maybe Round can share more about the constrains of his environment.

Amir.
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