Category Archives: Linux

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

Enable transmission-daemon logging to file

If you use transmission-daemon on your Raspberry Pi and want to have logs to a file, you can follow a few simple steps to accomplish this:

Edit the service file:

Change the ExecStart line to look like this:

You can choose between these options:

systemctl will complain that the service file was changed. Run:

to reload units.

Create the log file and assign the correct ownership and permissions:

Restart the service:

Have fun!

Add syntax color to crontab editor

You might be wondering why you don’t have syntax coloring when you are editing crontab entries.
This can be solved very simply by specifying your editor before starting crontab:

The change can be made persistent across the whole system if you add that line on the /etc/bashrc file.
You you only need this change for certain users only, add the line to their local ~/.bashrc files.

Disable recent documents in Gtk2/Gtk3

Use the following to disable recent documents in Gtk2/Gtk3:

The ugly part is that there is no way one can disable ‘Recently Used’ in the GtkFileChooser dialog box.


screenshot-20120307@111318

Quick way to convert Mbox mailboxes to Maildir format

A quick way to convert Mbox mailboxes to Mbox format is to use mb2md.
Install it in Ubuntu/Debian using:

To make the convertion use:

From man:

Nice and simple!

Bash script to backup my configs (dotfiles)

I needed some script to take care of my config files and put them in a single directory. So here it is.

Moved to ArchLinux!

Moved my ThinkPad T61 to ArchLinux! (Still using Ubuntu on many other machines.)

Screenshot:
2011-06-16-215838_1680x1050_scrot
I will post some install script I used to configure my system.

Liferea custom stylesheet

I don’t like very much the default font used by Liferea, so I decided to use my custom font. Here is how:
1. Copy the default stylesheet to liferea folder in my $HOME:

2. Add this:

at the begining of liferea.css file.

This is how it looks now:
screenshot-20110616@203706

Of course, you can also play with all the other options in the liferea.css.
Have fun!

Just installed Archlinux on my ThinkPad T61

I’ve installed Archlinux on my ThinkPad T61 about a week ago and so far I am impressed.
I will post more info about the tweaks and customisations I’ve done to make everything work.
Check out the screenshots page.

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