[GTALUG] Compressing an image of a microSD card

[William Park]

On Thu, May 14, 2020 at 03:38:37PM -0400, Lennart Sorensen via talk wrote:
> >  * Loop mount, e.g. 'mount -o loop,offset=$((512 * xxxx))
> >    RG350.SD.2020-05-14.img tmp/' where xxx is the number of, e.g.,
> >    512-byte sectors
>
> If you enable partition support on your loop driver you don't need to
> deal with the offset calculations and such.  It is unfortunately not
> enabled by default for legacy reasons I believe.
> 
> modprobe -r loop
> modprobe loop max_part=16
> 
> Then losetup /dev/loop0 imagefile
> 
> and you should have /dev/loop0p1 /dev/loop0p2 etc.
> 
> If the filesystem is ext based, zerofree is a nice tool to zero unused
> space that seems to run faster than using dd and rm with a zero filled
> file.

I had to do this kind of thing before, but I don't remember loading
"loop" module with options.  I think "losetup" does it or with some
options.
-- 
William Park <opengeometry at yahoo.ca>