Tag Archives: MSSQL

Configure Active Directory authentication with SQL Server on Linux

Microsoft just released the adutil in public preview which is a CLI based utility developed to ease the AD authentication configuration for both SQL Server on Linux and SQL Server Linux containers.

We don’t need to switch to a Windows machine to create the AD user for SQL Server and setting SPNs.

In the following steps I will try to install a SQL Server instance on Linux using just the Linux CLI tool adutil.

We will need 2 VMs:
  • tf-wincore01.lab.local – Domain Controller (DC) running on Windows Server 2019 Core (will
    host the lab.local domain)
  • tf-ubuntu01.lab.local – Ubuntu 18.04 LTS – SQL Server Instance on port 20001 will be
    installed here

I will be creating a brand new environment for this test and I am using Terraform to provision the VMs .

Prepare the Domain Controller

Once the VMs are created we need to configure the domain controller:

Let’s setup our zones:

Note that this AD configuration is just the bare minimum for our lab and it’s not fit for a Production environment!

Join the Linux host to the domain

It’s now time to join the Linux box to our new domain. The yaml file used by netplan needs to point to the domain:

Confirm the configuration and apply it.

In my case, the file looks like this:

/etc/resolv.conf file should also point to the domain:

Next, we install the packages that will allow us to join the machine to the domain:

Let’s also set the hostname:

We are now ready to join the machine to the domain:

This command:

  • creates a new computer account in AD
  • creates the /etc/krb5.keytab host keytab file
  • configures the domain in /etc/sssd/sssd.conf
  • updates /etc/krb5.conf

Let’s verify that we can now gather information about a user from the domain, and that we can acquire a Kerberos ticket as that user. The following example uses id, kinit, and klist commands for this.

Install adutil

We now need to install the adutil so we can interact with the Domain Controller directly from the Linux box.

Create a domain user using adutil

Let’s try to create a regular AD user:

At this point adutil cannot list the users, but we can check if an account exists in the AD

Install SQL Server instance on the Linux host

From this point on, I can proceed at installing the SQL Server instance on the Linux host:

Create an AD user for SQL Server and set the ServicePrincipalName (SPN) using adutil

SQL Server instance is running and let’s now create an AD user for SQL Server and set the ServicePrincipalName (SPN) using the adutil tool.

Test the connections and the authentication scheme

Let’s create an AD-based SQL Server login:

Connecting as a domain user from the Linux box:

Let’s verify the authentication scheme:

Conclusion

Our setup is now complete and we managed to perform all the required operations from a Linux machine. The same can be applied to provision SQL Server running on Linux containers. This also should apply if you’re running in the cloud.

Always On Availability Groups using containers

The complete code can be found on my GitHub account

As a SQL Server person, I usually need to work with full blown Availability Groups for my various test scenarios.
I need to have a reliable and consistent way to rebuild the whole setup, multiple times a day.

For this purpose, docker containers are a perfect fit.
This approach will serve multiple scenarios (tsql development, performance tuning, infrastructure changes, etc.)

Target

Using the process I’ll explain below, I will deploy:

  • 3 nodes running SQL Server 2019 Dev on top of Ubuntu 18.04
  • 1 Clusterless Availability Group (also known as Read-Scale Availability Group)

Note that our Clusterless AG is not a high availability or disaster recovery solution.
It only provides a mechanism to synchronize databases across multiple servers (containers).
Only manual failover without data loss and forced failover with data loss is possible when using Read-Scale availability groups.

For production ready and true HA and DR one should look into traditional availability groups running on top of Windows Failover Cluster.
Another viable solution is to run SQL Server instance on Kubernetes in Azure Kubernetes Service (AKS), with persistent storage for high availability.

How

The workflow consist of the following steps:

  • prepare a custom docker image running Ubuntu 18.04 and SQL Server 2019
  • create a configuration file that will be used by docker-compose to spin up the 3 nodes

 

 

 

 

 

The actual build of the Availability Group will be performed by the entrypoint.sh script that will run on all the containers based on the image we just created.

The entrypoint.sh file is used to configure the container.
We just need to add a few .sql scripts that will get executed using sqlcmd utility.
In this case is the ag.sql file that contains the commands to create logins, certificates, endpoints and finally the Availability Group.

Remember, we’re using a Clusterless Availability Group, so the SQL Server service on Linux uses certificates to authenticate communication between the mirroring endpoints.

In a matter of minutes I have a fully working AG.

Credentials

During the build of the docker image and to create the AG I will need to specify various variables and credentials.

For production environments the recommended approach to manage secrets is to use a vault.

For my case I’m storing various variables and credentials in plain text files in the env folder.
Docker will parse those files and they will be available as environment variables.

  • sapassword.env – this contains the SA password and it’s needed when the custom image is built.

  • sqlserver.env – various variables are set here and are needed when the custom image is built.

  • miscpassword.env – will be needed to create the login and certificate needed by the Availability Group. This file is actually added to the container and it will be deleted after the Availability Group is created.

The advantage of this approach is that I have only one place where I store all these variables and credentials, but as I mentioned earlier, it’s not a proper solution from a security standpoint.

A few alternative approaches would be:
– use a tool to manage secrets, like Vault
multi-stage builds
– use BuildKit

Conclusion

From a testing and development point of view, this solution works very well for me as I can rebuild the environment in a fast and consistent way.

It’s not by any means the best option out there, but it’s really simple to use and reproduce.

See it in action

Click on the image for the full gif

Wrong network location profile causes issues with Windows Failover Cluster

Hi folks,

The other day I was pulling hair from my head trying to configure a Windows Failover Cluster intended for an SQL Server Availability Group setup.

During the cluster validation stage I always got this message:

The Windows Firewall on node node01.domain.local is not properly configured for failover clustering.
In particular, the ‘Public’ firewall profile is enabled on adapter ‘node01.domain.local – SLOT 1 PORT 2’.
The ‘Failover Clusters’ rule group is not enabled in firewall profile ‘Public’.
This may prevent some network communication between cluster nodes.

The OS install and networking part was already configured by a someone else and it was a pretty straightforward installation.

The issue turned out to be caused by the 2 NICs we have for iSCSI traffic which did not have a gateway configured.

Windows uses gateways to identify networks. If it doesn’t have a gateway configured, or if it can’t successfully ping it, it will not be able to identify the network it’s connected to and will assume it’s a public one.

Network cards in Windows can be connected to one of these type of networks:
– Public
– Private
– DomainAuthenticated

By default, the public network location type is assigned to any new networks when they are first connected.

A public network is considered to be shared with the world, with no protection between the local computer and any other computer. Therefore, the Windows Firewall rules associated with the public profile are the most restrictive.

As part of the Windows Failover Cluster validation/creation there are checks to verify connectivity (between cluster nodes, active directory, etc.).

These were the settings I had:
Before

All I needed to do was to move all non-domain network interfaces into the private profile:

After

After the change the cluster creation went without issue.

This small detail be easily missed and can cause a lot of headaches and lost time investigating failover clusters.

Cheers!

Beautify SQL code

Recently I had the oportunity to test SQL Pretty Printer (Add-In for SSMS). I don’t have to waste time formatting long sql queries. In no time, SQL Pretty Printer does the job
for me. It can also translate the sql code into C#, Java, Php and many other program languages so I can use it in my own programs.
SQL Pretty printer is designed to deal with SQL statement used by different Database Such as MSSQL, Oracle, DB2, Informix, Sybase, Postgres, MySQL and so on. The code conforms to most of the entry-level SQL99 Standard.
To use this add-in you need to have SQL Server Management Studio (SSMS), with .NET2.0 installed. In sql editor you can use shortcut key (ctrl+k,ctrl+j for all sqls, and ctrl+k, ctrl+h for selected sql). There is also a toolbar with two buttons to format sql or selected sql.
To see it in action, take a look here, where you have some sample code blocks before and after the formatting.
sql_01
sql_02
sql_03

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close