Almost as simple as a standard copy command:
$ docker cp messages:/home/virgo/ /tmp
This docker command copies the Virgo Server located in the directory /home/virgo/ from inside the messages container to the /tmp folder of the current system. This allows to investigate the Virgo container locally:
$ cd /tmp/virgo
$ ./bin/startup.sh -clean
Note: Since the installation directory of the Virgo container changed you need to add the -clean flag.