ubuntu@box166:~$ docker run -ti --rm --read-only busybox
/ # touch /test
/ # ls /test
Expected:
/ # touch /test
touch: /test: Read-only file system
The same thing happens on Docker version 1.8.2-circleci-cp-workaround, build 4008b9c-dirty as well as Docker version 1.10.0-circleci, build 543ec7b-unsupported.