On 2011-07-25, at 7:39 PM, Yongqiang Yang wrote:
> On Mon, Jul 25, 2011 at 9:10 PM, Ted Ts'o <tytso@xxxxxxx> 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
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