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Category: Containers

Creating Docker Volumes

Published 2017-06-29 by Kevin Feasel

Andrew Pruski continues his series on long-term data storage and Docker:

Awesome stuff! We’ve got a database that was created in another container successfully attached into another one.

So at this point you may be wondering what the advantage is of doing this over mounting folders from the host? Well, to be honest, I really can’t see what the advantages are.

The volume is completely contained within the docker ecosystem so if anything happens to the docker install, we’ve lost the data. OK, OK, I know it’s in C:\ProgramData\docker\volumes\ on the host but still I’d prefer to have more control over its location.

It’s worth reading the whole thing, even though this isn’t the best way to keep data long-term.  It’s important to know about this strategy even if only to keep it from accidentally ruining your day later.

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Persisting Containerized Data

Published 2017-06-22 by Kevin Feasel

Andrew Pruski has started a series on persisting data in Docker containers.  He starts off the series with an easy method of keeping data around after you delete the container:

Normally when I work with SQL instances within containers I treat them as throw-away objects. Any modifications that I make to the databases within will be lost when I drop the container.

However, what if I want to persist the data that I have in my containers? Well, there are options to do just that. One method is to mount a directory from the host into a container.

Full documentation can be found here but I’ll run through an example step-by-step here.

Statefulness has been a tough nut to crack for containers.  I’m interested in seeing what Andrew comes up with.

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Moving Docker Containers

Published 2017-06-14 by Kevin Feasel

Andrew Pruski shows how to change the default location for Docker containers on Windows:

There’s a switch that you can use when starting up the docker service that will allow you to specify the container/image backend. That switch is -g

Now, I’ve gone the route of not altering the existing service but creating a new one with the -g switch. Mainly because I’m testing and like rollback options but also because I found it easier to do it this way.

Read the whole thing.

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Jupyter And Kubernetes

Published 2017-06-05 by Kevin Feasel

David Crook shows how to use Jupyter notebooks inside Kubernetes:

We start with a 16.04 image, we run some upgrades, install python, upgrade pip, install our requirements and expose port 8888 (jupyter’s default port).

Here is our requirements.txt file

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numpy
pandas
scipy
jupyter
azure_common
azure-storage
scikit-learn
nltk
plotly

Notice how Jupyter is in there, I also added a few other things that I very commonly use including numpy, pandas, plotly, scikit-learn and some azure stuff.

The big benefit to doing this is that your installation of Jupyter can exist independently from your notebooks, so if you accidentally mess up Jupyter, you kill and reload from the image in a couple commands.

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SQL On Docker Environment Variables

Published 2017-05-22 by Kevin Feasel

James Anderson lists the current environment variables that you can set for a SQL Server on Linux Docker container:

As of CTP 2.1 for SQL Server 2017 a set of new environment variables are available. These variables allow us to configure each SQL Server container as we spin them up. The first version of SQL Server on Linux came with:

ACCEPT_EULA
SA_PASSWORD

These had to be set for the container to start. The SA_PASSWORD has be a complex password or the container will not start. CTP 2.1 introduced:

Read on for the new variables and an example on how to use them.

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File Management In Containers

Published 2017-05-12 by Kevin Feasel

Andrew Pruski hows how to copy files into and out from Docker containers:

Last week I was having an issue with a SQL install within a container and to fix I needed to copy the setup log files out of the container onto the host so that I could review.

But how do you copy files out of a container?

Well, thankfully there’s the docker cp command. A really simple command that let’s you copy whatever files you need out of a running container into a specified directory on the host.

I’ll run through a quick demo but I won’t install SQL, I’ll use an existing SQL image and grab its Summary.txt file.

Read on for the demo.

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Attaching A SQL Server Database To A Docker Container

Published 2017-05-09 by Kevin Feasel

Mat Hayward-Hill shows how to attach an existing MDF file to a SQL Server on Linux instance in Docker:

Now we are ready to attach the database using the TSQL below. For this demo, I used Management Studio from my Laptop, to connect to SQL Server.

In the TSQL we need to use the FOR ATTACH_REBUILD_LOG argument as we have no log file to attach. It will create a 1MB log file in the default log file directory.

It’s better to restore a full backup, but there’s more than one way to connect a database.

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Building A SQL Server 2014 Container

Published 2017-05-03 by Kevin Feasel

Andrew Pruski shows how to create a Docker container with SQL Server 2014 SP2 installed:

I’m running all of this on my Windows 10 machine but there are a few things you’ll need before we get started: –

Pre-requisites

  • The microsoft/windowsservercore image downloaded from the Docker Hub

  • Windows Server 2016 installation media extracted toC:\Docker\Builds\Windows

  • SQL Server 2014 SP2 Developer Edition installation media extracted to C:\Docker\Builds\SQLServer2014

Or if you prefer, you can just pull his image, but where’s the fun in that?

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Connecting Powershell To Docker Containers

Published 2017-04-06 by Kevin Feasel

Andrew Pruski shows how to open a Powershell session on a container:

One of the questions that I was asked at SQL Saturday Iceland was “how can I view the filesystem within a container?”.

This is a great question as one of the things that people find off-putting about containers is their opaqueness. It’s not obvious where everything lives within the container or how we can view the files within it.

Thankfully there’s a simple docker command that allows us to open a powershell session within a container, that command is docker exec.

For Linux-based containers, /bin/bash (or your favorite shell, if it’s installed) serves as its analog.

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Dockerizing Windows Applications

Published 2017-03-13 by Kevin Feasel

Elton Stoneman has a five-step process for turning your Windows app into a containerized application:

1. Choose Your Base Image

Docker images for Windows apps need to be based on microsoft/nanoserver or microsoft/windowsservercore, or on another image based on one of those.

Which you use will depend on the application platform, runtime, and installation requirements. For any of the following you need Windows Server Core:

  • .NET Framework apps
  • MSI installers for apps or dependencies
  • 32-bit runtime support

For anything else, you should be able to use Nano Server. I’ve successfully used Nano Server as the base image for Go, Java and Node.js apps.

This is good reading if you’re thinking of offering a containerized version of your product.

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