I could not get the mount command to work without specifying the dev block to mount as /system
#cat /proc/mounts
returns ( only the system line here )
/dev/stl12 /system rfs ro,relatime,vfat,log_off,check=no,gid/uid/rwx,iocharset=utf8 0 0
so my working command is
mount -o rw,remount -t rfs /dev/stl12 /system