This question is very simple: Who are you? Unfortunately, the answer is not so simple. The database engine needs to verify your identity, and I believe a more important question is Is this really you?

During the setup procedure, you have to select a sa password which actually uses the SQL Server authentication process. This database engine comes from Windows and it is tightly connected with Active Directory and internal Windows authentication. In this phase of development, SQL Server on Linux only supports SQL authentication.

Figure 8-1. Authentication process

SQL Server has a very secure entry point. This means no access without the correct credentials. Every information system has some way of checking a user's identity, but SQL Server has three different ways of verifying identity, and the ability to select the most appropriate method, based on individual or business needs.

When using SQL Server authentication, logins are created on SQL Server. Both the user name and...