Category: Containers

Andrew Pruski helps out those of us who can’t seem to let our containers go:

One of the problems that I’ve encountered since moving my Dev/QA departments to using SQL Server within containers is that the host machine is now a single point of failure.

Now there’s a whole bunch of posts I could write about this but the one point I want to bring up now is…having to start up all the containers after patching the host.

I know, I know…technically I shouldn’t bother. After patching and bouncing the host, the containers should all be blown away and new ones deployed. But this is the real world and sometimes people want to retain the container(s) that they’re working with.

It’s pretty easy to set up a restart policy, as Andrew shows.

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 We would no longer have to worry about any containers running SQL instances with databases that are out of date.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.