RPi OverlayFS and read-only also turns external mounted drive read-only/root-only

Question

Background

I have recently discovered and experimenting with OverlayFS setting in raspi-config on RPi3 with openmediavault. I am trying OverlayFS because system on sdcard is way too fragile. So far, this feature is able to prevent sdcard from failing.

Issue

The external HDD mounted seems to be "read-only" after the activation of OverlayFS. More accurately, the external drive is root-only where it is writable with sudo or under sudo su. This is rather inconvenient since this system is configured as media hub and it doesn't make sense to use super user access for everything.

All the directories and files in the drive seems to be in drwxr-xr-x and root as owner and group (I didn't pay attention if it is the same case when OverlayFS is activated)

Progress and Attempts

• I tried adding rw in /etc/fstab and mount -a to remount. But it is still unwritable to others.
• sudo chmod +w executes but no effect is taken.
• sudo chown pi:pi results in Operation not permitted
• modify /etc/fstab to include rw,nofail, drive is still about to root-only access.

Questions

I am still learning the nature of OverlayFS + read-only setting and I have the following questions:

1. Is it because of OverlayFS + read-only setting that external drive is mounted with root-only access?

2. Is it possible to use OverlayFS + read-only with writeable external drive?

3. If that's not possible, any other trick to protect sdcard while writable to external drive?

Any suggestion is appreciated ~