Migrate from Windows to Linux
You cannot run/install SQL Server 2008 or any other production version on Linux OS, this is not allowed or possible, you can only install it on Windows server/client OS. 

As per their official Blog, Microsoft announced in March 2016 that is planning to launch SQL Server on Linux: Announcing SQL Server on Linux. The SQL Server version is currently called v.next and will be available on Linux. Tentative date for release is Mid 2017.

There is a public preview version that can be installed/tested now but is not production ready yet: Take a closer look at SQL Server on Linux