$ wget https://releases.hashicorp.com/vagrant/1.8.1/vagrant_1.8.1_x86_64.deb \
> -O /tmp/vagrant_1.8.1_x86_64.deb && \
> [sudo] dpkg -i $_
Another solution is to use this unofficial repository.
$ wget https://releases.hashicorp.com/vagrant/1.8.1/vagrant_1.8.1_x86_64.deb \
> -O /tmp/vagrant_1.8.1_x86_64.deb && \
> [sudo] dpkg -i $_
Another solution is to use this unofficial repository.