How do check ubuntu is using the correct package repository?

petulia3478

Man: http://lightnetics.nodebb.com/post/853

$ sudo apt-cache policy docker-engine
docker-engine:
  Installed: (none)
  Candidate: 1.8.3-0~trusty
  Version table:
     1.8.3-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
     1.8.2-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
     1.8.1-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
     1.8.0-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
     1.7.1-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages
     1.7.0-0~trusty 0
        500 https://apt.dockerproject.org/repo/ ubuntu-trusty/main amd64 Packages