I require symlinks in the user portion of my android storage. Turns out it’s a lot more complex than that.

Current phone has internal storage only (also known as a mistake), so this might be a bit simplified.

Actual user storage files are on an ext4 partition at /data/media/0 It’s emulation mounted to other places, and eventually put at places like /storage/self and /sdcard with a bunch of per-user/per-app sandboxing. Actual explanation on stack overflow.

Symlinks in /data/media/0 work there, but in the sdcardfs bind mounts that are pretending to be a fat filesystem, they just show up as files.

Bind mounts work though.

So to make one directory show up in another place, what I ended up with was

mount --bind /data/media/0/DCIM/Camera/office_lens/ /data/media/0/Pictures/Office\ Lens

Turns out that only works in adb shell because that’s in the global mount namespace.

Luckily, reddit user agnostic-apollo mentions that su --mount-master will drop us into the global mount namespace as well.

su --mount-master -c "mount --bind /data/media/0/DCIM/Camera/office_lens/ '/data/media/0/Pictures/Office Lens'"

To bind this on boot, I tried putting it in /data/adb/service.d/bind-mounts.sh according to magisk docs. Unforunately, /data/media/0 doesn’t seem to be mounted at the point that runs.

The end solution was a tasker shell task, running as root.