Containers:
Containers are a way to virtualize a single application, as opposed to virtualizing an entire server. We can run an application in this container without installing the product or worrying about all of the dependencies of that application. Everything needed to run an application is in the container.
Docker:
Docker is the most popular platform for running and managing containers.
Prerequsites for Installing Docker:
To install Docker on Windows, we’ll need to have Microsoft Windows 10 Professional or Enterprise 64-bit(You can also run on Windows Server), we need a version that will support virtualization. We also need virtualization enabled on the machine (You’ll need to go into the BIOS to enable this).
We’ll need Hyper-V and Containers features enabled as well. We can do this in the Control Panel, or use Cortanta to search for ‘Turn Windows features on and off’. Make sure the Containers and the Hyper-V items are checked. The Docker installation will check to see if these features are enabled, and will give you the option to enable these features then, but setting these before hand will save you a reboot.
Notes that if Hyper-V is enabled, then Virtual Box will not work, if you have that installed.
Installing Docker:
The Docker Community Edition for Windows is a free download, but you’ll need to set up a Docker login.
The install is pretty straight forward. For my example, I checked to Use Windows containers instead of Linux containers.
Basic Docker Commands:
We can use the Command Prompt or the Powershell Window to run Docker command, I used Powershell for these examples.
docker --version
: This will return the version and build number for the Docker install.
docker --help
: This will give us a list of available Docker commands. We can also use this to get additional information on a specific command, for example if we wanted more information on the version command, we would run docker version –help.
Sample Docker Container:
We can run a sample Hello World container just to make sure everything is set up on running correctly. We can run the command:
docker run hello-world
This will pull down the Hello World image and run it. If everything is running correctly, you’ll see a message ‘Hello From Docker!’. If things aren’t set up correctly you’ll see an error message.
Initially I got an error:
“container xxx encountered an error during CreateContainer: failure in a Windows system call: No hypervisor is present on this system.”
I had let the Docker install enable the Containers and Hyper-V components for me. When I went to check on the options, The Hyper-V Platform option under Hyper-V was greyed out with the message “Hyper-v cannot be installed: Virtualization support is disabled in the firmware”. It turned out that Virtualization was turned off on my laptop, which prevented this option from being enabled. I didn’t get an error during the install when it trying to enable these features, and it took me a while to figure out the issues. So I would recommend running through the prereqs yourself, instead of relying on the install to do this.
Other Docker Commands:
docker images
: List all of the installed images.
docker rmi hello-world -f
: To remove an image (hello-world). The -f flag will force removal.
docker container ls
: List running containers
Running SQL Server:
Now to a more practical use. We can run SQL Server in Docker. A container for SQL Server Developer edition is available through Docker Hub . We can view some information on the container here.
We can run this command to download the container:
docker pull microsoft/mssql-server-windows-developer
The download is 4-5 gigs.
Once we have pulled the container down, we can start it up:
docker run -d -p 1433:1433 -e sa_password=WeakPW12 -e ACCEPT_EULA=Y microsoft/mssql-server-windows-developer
It will take a few seconds to start up. Once the container is running, we’ll see an ID printed to the console. Make a note of this ID.
So there are a few parameters that have been set in the run command. -d means detached, which means that the container runs in the background. -p (for publish) designates the port for the service, we’ll stick with the SQL Server default of port 1433. We list two ports, one for the container and another for the host. -e will set an environment variable, in this case we’ll indicate that we accept the user agreement. We’re also using -e to set the sa password for this session. At first, I set a very simple sa password, and then I had issues trying to connect to SQL Server. When creating the sa password, you’ll have to follow the complexity requirements for a sa password, you won’t get an error message for an invalid password. The sa password has a 8 character minimum, plus you’ll need at least 3 from upper case letters, lower case letters, numbers and special characters.
We can connect to our SQL Server container either with the SQLCMD command line tool, or with SSMS. For this example, we’ll use SSMS.
To connect with SSMS, we’ll need to get the IP address for our running SQL Server. Using the ID we got when starting the container, we’ll run this command:
docker inspect {ID}
You can also use the 12 character Container ID. We can get that ID by running:
docker ps
In the output, we’ll go to Network Settings / Network / IP Address , and make a note of this address.
To connect with SSMS, we’ll use the IP Address as the Server Name (include a comma then the port number if not using the default port). Select SQL Server Authentication, then use sa and the sa password we passed in when starting the container.
Once we’ve connected, we can use SSMS to create objects, or open a query window, just as we would with any SQL Server.
Once we’ve completed, we can stop the container passing in the Container ID for {ID}:
docker stop {ID}
Once we stop the container, we’ll lose whatever objects and data that we’ve set up. It is possible to map the container to use data and log files on the host machine, this page goes through the setup for that.
Links:
Get started with Docker
Windows Containers
Docker Documentation
SQL Server 2016 Express Edition in Windows containers
Posted by Rob 