This issue tracks a second phase of jrt fs where we need to add support for creating a jrt file system that provides access to a target image.

As things stand then the current solution allows a tool on JDK 9 to create a jrt:/ for the current image and it allows a tool on JDK 8 to create a jrt:/ for a target JDK 9 image.

We need to improve the solution so that there is a way to specify the target image and to use the file system provider in the target VM. One option on the table is to extend the URI syntax to allow for the encoded java.home, another option is to specifying the java.home via a key in the newFIleSystem(URI, Map) call. Either way, creating a jrt:/ in this manner needs to transparently load the file system provider located in the target image, even if there is a jrt file system provider installed in the current image (so some amount of forwarding will be required to get this to work).