Download mssql from the microsoft website.
wget https://packages.microsoft.com/ubuntu/16.04/mssql-server/pool/main/m/mssql-server/mssql-server_14.0.1.246-6_amd64.deb
dpkg -i mssql-server_14.0.1.246-6_amd64.deb
The next command will install dependancies.
sudo apt-get -f install