"[Freetds][Sql Server]Adaptive Server Connection Failed" Error When Attempting To Connect To Ms Sql Via Kerberos Runas Authentication

Published: 11 Mar 2020
Last Modified Date: 08 Jul 2022


When attempting to access a SQL Server data source via the Kerberos Service Account on a Linux platform, the following set of errors may be returned through either a live connection or extract refresh failure:
"There was an unknown connection error to the database. The error message below has additional information, but you might need to ask the database administrator to review the database logs."
"[FreeTDS][SQL Server]Unable to connect to data source"
"[FreeTDS][SQL Server]Adaptive Server connection failed"  <- must exist in error text for this article to apply
"Unable to connect to the Microsoft SQL Server server \"<SQL SERVER>". Check that the server is running and that you have access privileges to the requested database."

Additionally, the following error may be logged in SQL Server logs:
"The login packet used to open the connection is structurally invalid; the connection has been closed. Please contact the vendor of the client library. [CLIENT: <MSSQL_IP>]"



  • Tableau Server
  • Microsoft SQL Server
  • Linux


Check with the DBA to verify the Service Principal Name (SPN) has been setup correctly for Kerberos authentication.



Service Principal Name (SPN) has not been configured properly for Kerberos authentication between SQL Server and Linux hosts.

Additional Information

The connection may work on Tableau Desktop and the connection to SQL Server live and refresh extracts successfully through a Windows PC by selecting "Windows Authentication".
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