why are there different images based on sd card size?

[checktravis]

I'm new to this, but have been exploring and experimenting with my new pine64 and also a rpi3 (just ordered a ODROID-C2 to play with as well). 

I haven't seen this practice elsewhere. for other distros I have tried there is a single img file and, once you have it flashed, you expand the file system to free up the rest of the card.

Just curious what the advantage is here.

thanks

[Ghost]

I'm new to this, but have been exploring and experimenting with my new pine64 and also a rpi3 (just ordered a ODROID-C2 to play with as well). 

I haven't seen this practice elsewhere. for other distros I have tried there is a single img file and, once you have it flashed, you expand the file system to free up the rest of the card.

Just curious what the advantage is here.

thanks

Expanding the file system utilised by the Android image is apparently trickier than your standard Linux image. The PhoenixCard version of the image expands readily enough, but not everyone gets on well with the PhoenixCard software, so there are also offered DD images, which can be burned using the dd command, or with software such as Win32DiskImager, ApplePi Baker or Etcher, depending on the computer you are using to burn the image.

See also this thread: Empty space.

Ideally I suppose the DD Android images would come with a built-in script that automatically expands the filesystem to fill the microSD card. Then only a single minimally-sized image would be needed.

[xalius]

Theoretically the /data partition on the dd images can be expanded since it is behind all the other ones. Practically the partition layout has overlapping definitions as I pointed out in http://forum.pine64.org/showthread.php?tid=1834 . I managed to resize the /data partition to the full size, but you have to use low-level tools like sfdisk since all the more user-friendly ones don't operate on partition tables with overlapping partitions. Maybe this can be somehow fixed in the build config of the Android SDK?

The Phoenixcard images are expanded on the fly to the full card size, but they require a tool that basically runs only on Windows and doesn't always work for everyone...