Why is my overlayfs command not working?

The commands below should be creating a root overlay, such that any modifications to root will appear in /tmp/upper However as you can see it does not appear to be working. Can anyone suggest what I am doing wrong? I am following the syntax here: https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt thanks ubuntu@ip-10-0-0-48:~$ sudo su root@ip-10-0-0-48:/home/ubuntu# cd /tmp root@ip-10-0-0-48:/tmp# mkdir upper root@ip-10-0-0-48:/tmp# mkdir workdir root@ip-10-0-0-48:/tmp# mount -t overlay overlay -olowerdir=/,upperdir=/tmp/upper,workdir=/tmp/workdir / root@ip-10-0-0-48:/tmp# touch /floob root@ip-10-0-0-48:/tmp# ls / bin boot dev etc floob home initrd.img lib lib64 lost+found media mnt opt proc root run sbin snap srv sys tmp usr var vmlinuz x root@ip-10-0-0-48:/tmp# ls /tmp/upper/ root@ip-10-0-0-48:/tmp#