How to use SD card formatted as internal storage for arbitrary data?

Question

On an LG V30 with 64GB internal memory I wanted to be able to use a 200GB SD card (which strangely gets reported as 256GB) to store larger amount of data like pictures, music and movies.

I learned that with Lineage OS 16 (Android 9 Pie) you cannot use your SD card as before since apps are no more allowed to write data to SD cards (is there an Apple manage working at Google now?!)

I then formatted my SD card as "internal storage" (believing that it now extends my 64GB to 200GB) but there doesn't seem to be a way to move arbitrary date to this new "internal storage".

So my (still very fuzzy) question is: is there a way to use an SD card to store arbitrary (i.e. not owned by one app) data like a Movies, Pictures etc. folder (which might be synced automatically by Syncthing or similar apps)?

(extra question: can formatting an SD card as internal storage be undone?)

Android rounds-off storage size to nearest power of 2. So 200 would be becoming 256. Apps aren't allowed to write directly to external SD card since KitKat at least; they hired Apple managers long time ago ;) That's why SAF was introduced which is extended in 5, 7 and now in 10. You must already be saving arbitrary data to Adopted SD card. Check with df if it's /mnt/expand/[UUID] mounted on /storage/emulated. — Irfan Latif, Sep 25 '19 at 20:03
I don't know if I really get it.. Can I relocate Pictures, Downloads or Music to the adoptable storage? And is there a way to comfortably access data @ /mnt/expand/[UUID] (i.e. without having to lookup and re-enter this ugly path again and again)? — frans, Sep 25 '19 at 20:30
Possible duplicate of How to free Internal Storage by moving data or using symlink / bind-mount with Adoptable Storage? — Irfan Latif, Oct 19 '19 at 23:41

How to use SD card formatted as internal storage for arbitrary data?

0 Answers0