Category: Containers

Andrew Pruski explains how to use Watchtower to keep your SQL Server Docker containers up to date:

The databases that I store in my container image are updated on a weekly basis and currently, the process to update our containers is manual. Once the updated image has been created, the existing running containers are dropped and new ones created from the updated image.

But what if we could automatically refresh our containers with the updated image? If we could do that then the only process that’s manual is updating the image. We would no longer have to worry about any containers running SQL instances with databases that are out of date.

Luckily, there’s a way to do this and it’s accessible via an image on the Docker Hub called Watchtower. What Watchtower does is monitor the Docker Hub and if there’s an update to an image it will automatically refresh all running containers that are on the same host.

Read on for a step-by-step solution.

Andrew Pruski shows how to use Docker compose to build multiple containers simultaneously:

As SQL Server people we’re only going to be interested in one application but that doesn’t mean we can’t use compose to our advantage.

What I’m going to do is go through the steps to spin up 5 containers running SQL Server, all listening on different ports with different sa passwords.

Bit of prep before we run any commands. I’m going to create a couple of folders on my C:\ drive that’ll hold the compose and dockerfiles: –

Andrew also explains a couple of common errors as he walks us through the process.

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.

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.

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.