If you need to add a full text search index on you column, then you need to add an extra package. You can install it by using the following command:

yum -y install mssql-server-fts

If the package is not found, then you need to go to Windows Docs to install the required repository.

After that you just to need to restart the sql server:

systemctl reload mssql-server

And you will have your full text search feature enabled. You can check the availability using following command in SSMS on mater database:

SELECT SERVERPROPERTY('IsFullTextInstalled') AS [Full Text Search Installed];  
GO

You will get the following result if fulltext search is available:

For Docker script check this link.