I'm testing with a real sd card, and it's behavior is not satisfying.
I can't tell how this works on other devices, but on a H2O, it works this way:
If I'm adding a real SD card, then it's content is processed by nickel. The new books appear in the library. I put some in collections, open them, make annotations, etc. If I remove the card and later insert it again, the collections, read status and annotations remain. If then I unplug it, and mount a virtual sd to /mnt/sd/ using:
Code:
mount --bind /mnt/onboard/.mysd/ /mnt/sd
echo sd add /dev/mmcblk1p1 >> /tmp/nickel-hardware-status
Then it's content is processed by nickel, the same applies as a real sd card. If I "unplug" it with these commands:
Code:
umount /mnt/sd/
echo sd remove /dev/mmcblk1p1 >> /tmp/nickel-hardware-status
Then the books are removed from the library. If I later mount the virtual sd, then all the read status, annotations, etc. remain as with the real card.
BUT! If I mount the real sd after the virtual, or the virtual after the real, all the read status, annotations, etc. are removed from both the virtual and real sd, so I can't mix them.
If I'm mounting the virtual one to any subdir in /mnt/sd/, than both sd's read status, etc. are not kept, also if the virtual sd is not removed before inserting the real sd then the read stats, etc. are removed from both.
If I'm updating the database when virtual SD is used, then everything is kept, and treated like any other sideloaded content - after a nickel restart.
If anyone else could try these on other devices, please post your experience!