Docker on Debian testing

Hi All
Where is located this file on Debian (3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-2)? And Can I insert line, like for default configure bridge0:
ExecStart=/usr/bin/docker daemon -D --bridge=bridge0

The location for the docker.service systemd unit on my debian system is /etc/systemd/system/docker.service

You can indeed edit it to change the command line options that docker launches with.