I have a rooted phone running android 4.4. When I check the output of 'mount' it says system is read only. My root file manager or terminal can't make any files or folders there, though only the file manager shows an error occured.
But I found I am able to copy files from my data partition to system, even overwriting system files if I want to. Why is this?
Another odd thing I noticed is that the system applets like mount and mkdir are actually symlinks to a binary file called 'toolbox'. For some reason I am not able to remount the system partion with the normal syntax, it says invalid option (using -o remount,rw /dev/xxx/system /system). This is preventing me from installing busybox with an installer app.