How to automatic set chmod 750 to the external HD?

Hi guys,
I’ve changed the chmod of my external USB HD from 777 to 750 but when I reboot the Raspy it become 777 again… how can I set 750 as default in OSMC?

What filesystem is it formatted with ?

Linux (ext4)

This is done on purpose:

Without it, most people would not be able to write to an external ext4 drive as even the root directory of that drive would not be writable by the OSMC user.

Typically the root directory of an external ext4 drive is owned by root, so with default permissions only root would be able to write to it. This makes sense for an operating system boot drive holding the root file system, but not for a portable external data drive.

Can I ask why you’re trying to change it ? We only change the permissions on the root directory of the drive, (at the mount point) not any directories or files within it.

Thanks for really clear explanation.
It was my faut, sorry, I’ve changed a permisison for a folder inside the HD but I’ve made a mistake checking the permisison of another folder… everything works, sorry again!