Below are step by step process to downgrade Cumulative Updates(CU) in SQL Server on Linux and this CU downgrade is applicable for SQL Server having same version. Also, note that backward compatibility is still not supported, i.e. we can not downgrade from SQL Server 2019 to SQL Server 2017.

Run below query to check current SQL Server version.

SELECT SERVERPROPERTY('productversion') 'ProductVersion', SERVERPROPERTY ('productlevel') 'ProductLevel', SERVERPROPERTY ('edition') 'Edition'

SQL Server version/CU can be verified using OS level command as well. Follow this link to check SQL Server 2019 build version and its corresponding CU details.

sudo yum info mssql-server

From above output, it is clear that SQL server 2019 is currently running on CU17 and we will downgrade it to CU12. Below is the command to downgrade SQL Server CU

Syntax:

sudo yum downgrade mssql-server-<desired _version_number>.x86_64

Command:

sudo yum downgrade mssql-server-15.0.4153.1.x86_64

We can see that downgrade is completed now and we will verify Installed version by running below command. We will also verify by logging into SQL Server.

Below query can be used to check installed and available packages

sudo yum list mssql-server –showduplicates