how to set emmc to read-only


I got a NanoPi Neo Air and installed the following image to the emmc:

As I know, the emmc should not be written to often, so I would like to set
the OS to read-only to prevent damage.

My first try was to remount / with ro, but it doesn't work that easy...
mount -n -o remount,ro / 
mount: / is busy

I created /etc/fstab and changed it to:

/proc           proc    defaults              0 0
/dev/mmcblk0p1  /boot           vfat    ro           0 2
/dev/mmcblk0p2  /               ext4    ro,noatime   0 1
tmpfs           /var/log        tmpfs   nodev,nosuid          0 0
tmpfs           /var/tmp        tmpfs   nodev,nosuid          0 0
tmpfs           /tmp            tmpfs   nodev,nosuid          0 0

But / is still not mounted read-only.

I also read through that article, but it seams there are to many
differences to the image I uses.

Would be great to swap between read-only and write mode manually.
Finally, I would like setup a small webserver to control some IO Pins.

I have Serial and SSH access to the board. 

Would be great if anyone could help me :-)

Thanks a Lot


Click on "File Management" in the Windows Mobile Device Center main menu,
and then double-click your GPS system to open it in a new file browsing
window. Drag and drop the completed Windows CE installation file onto the
GPS device. When the file transfer is complete, disconnect your GPS device
from the USB cable.