Blank out Internal Monitor

I just installed LibreELEC-Generic.x86_64-11.0.3.img.gz on a laptop that is hooked up to my TV. However the video is only being displayed on the laptop monitor, in the past I was able to edit the syslinux.cfg and disable the internal display, however when I tried tonight through ssh it keeps telling me that syslinux.cfg is a read only file system and I can't seem to modify this file.

Found the fix was to remount the flash directory with permissions

need to remoint the flash directory with rw permissions then make changes and then remount with read only rights then reboot device

mount -o remount,rw /flash

nano syslinux.cfg

mount -o remount,ro /flash