Re: [gentoo-user] Creating an firmware image from a too large microSDcard...?

[Bill Kenworthy]

On 16/01/16 17:27, Neil Bothwick wrote:
> On Sat, 16 Jan 2016 04:50:49 +0100, Meino.Cramer@×××.de wrote:
>
>> to post a firmware image of my embedded linux computer
>> to a friend I want to size it down.
>>
>> System wise I did that already (only the really necessary
>> stuff of Gentoo plus some configuration and addons related
>> to the embedded system)...the problem comes with the size of
>> the microSDcard I use: 32 GB....
>>
>> The microSDcard (source) has two partitions (boot + the rest).
>> The boot partition is the first partition and it is of a fixed
>> and tiny size. The second partition contains the "rest": Gentoo.
>> Currently the used space of this partition is also small.
>>
>> The image needs to be of a format, which makes
>> it possble to 'dd' it onto a microSDcard (target) and afterwards use
>> g/parted to resize/expand the second partition to the end
>> of the microSDcard to get all storage space available.
>
> Quick and kludgy. Partition an SD card of the correct size, rsync your
> data to it, then dd that card.
>
> Any other method you use will require you to have a smaller SD card to
> test the resultant image, so you may as well use that as the source and
> know it works.
>
>

It is possible to create a dd image of the whole SD card and mount it in
a loopback to repartition etc.

Mount it then shrink your existing file system (and probably the
partition too) to less than the required size, then recreate the dd
image to a size still less than the new sd card.

On the new card, dd it across until it errors off, then fix/expand the
partition and then the file system.  You dont care if the end is missing
as long as your data is within the size needed.

BillK