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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 25 Jul 2011 22:07:19 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	Amir Goldstein <amir73il@...il.com>, "Ted Ts'o" <tytso@....edu>,
	Round Robinjp <roundrobinjp@...oo.co.jp>,
	linux-ext4@...r.kernel.org
Subject: Re: flashing large eMMC partitions with ext4

On 2011-07-25, at 7:39 PM, Yongqiang Yang wrote:
> On Mon, Jul 25, 2011 at 9:10 PM, Ted Ts'o <tytso@....edu> wrote:
>> On Sat, Jul 23, 2011 at 12:49:28AM +0900, Round Robinjp wrote:
>>> I have a question regarding making ext4 image for
>>> large eMMC partition.
>>> 
>>> We have a 4G partition in our embedded device
>>> in which we want to use ext4 filesystem.
>>> But for that we have to create a 4G image.
>>> flashing this 4G image to the eMMC takes a long
>>> time. Is there any way to reduce this time?
>>> 
>>> For vfat, you can truncate the image leaving only
>>> non zero-filled blocks which makes the image very
>>> short and the time for flashing is reduced.
>>> Is something similar to that possible for ext4?
>> 
>> I'm guessing the problem is you've already created a file system image
>> which is 4G, and for which a large number of the blocks are not used,
>> and you're trying to optimize the amount of time it takes to flash the
>> image.  Is that right?
> 
> Now the fs is clean, so we can delete journal.  After the image is
> flashed to the eMMC, we can add journal again.  I think tune2fs can
> add and delete journal.  Am I rgiht?

Yes, "tune2fs -O ^has_journal {dev}" will remove the journal (if clean).
That will save 32MB of space in your image.

Then, use "resize2fs -M {dev}" to shrink the image as small as possible,
and then after restoring the image, run "resize2fs {dev}" to grow the
image to fill the device again and "tune2fs -j {dev}" will add it again
with the default size.

Cheers, Andreas





--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html