Removing Business Central Docker containers with PowerShell

Yesterday I bumped into an intermittent issue on our Jenkins CI server where some Business Central containers where not getting removed after use. This led me to find a way of removing Business Central Docker containers with PowerShell, and a topic for a blog post. The issue seems to be with a process keeping the NavContainerHelper container folder open, which is stopping the script from removing it.. anyway, that’s not what this post is about.

As a temporary work-around while I get to the root cause of the issue, I decided to build the containers with a unique name and setup a nightly cleanup job to remove any surplus containers on the build server.

To do this, I first need a list of containers to remove. I used the docker ps command, formatting the result a a table to make it easier to use in PowerShell:

$containers = docker ps -a --filter "name=bc*" --format "{{.Names}}"

Filtering

I was using the prefix “bc” on my container names, so I’ve selected this as my filter “name=bc*”. You could also filter on the image using the ancestor filter. For example:

$containers = docker ps -a --filter "ancestor=mcr.microsoft.com/businesscentral/sandbox:gb-ltsc2019"

Unfortunately I couldn’t get the ancestor filter to work with a more generic image name (i.e. mcr.microsoft.com/businesscentral/sandbox) which limited it’s usefulness in my scenario.

There is also the label filter which is useful. The Business Central images come with a number of labels which we can retrieve by querying our containers. For example:

PS C:\WINDOWS\system32> docker ps -a --format "{{.Labels}}"
country=gb,tag=0.0.9.97,nav=,osversion=10.0.17763.914,platform=15.0.37865.39262,created=201912201932,cu=update31,eula=https://go.microsoft.com/fwlink/?linkid=86
1843,legal=http://go.microsoft.com/fwlink/?LinkId=837447,maintainer=Dynamics SMB,version=15.1.37881.39313
country=W1,legal=http://go.microsoft.com/fwlink/?LinkId=826604,maintainer=Dynamics SMB,nav=2018,tag=0.0.9.2,version=11.0.19394.0,created=201903101911,cu=rtm,eul
a=https://go.microsoft.com/fwlink/?linkid=861843,osversion=10.0.17763.316
cu=rtm,eula=https://go.microsoft.com/fwlink/?linkid=861843,legal=http://go.microsoft.com/fwlink/?LinkId=826604,maintainer=Dynamics SMB,nav=2018,country=gb,creat
ed=201903102009,osversion=10.0.17763.316,tag=0.0.9.2,version=11.0.19394.0

The above output shows a list of label key/value pairs being used by containers on my machine (I’ve only got Business Central and NAV containers). One label common to all my containers is “maintainer=Dynamics SMB”, which we could use in our filtering as follows:

docker ps -a --filter "label=maintainer=Dynamics SMB"

Formatting the output

After running the script (with –format “{{.Names}}”), $containers will look something like this:

bccontainer1
bccontainer2
bccontainer3

I only want the container name so I’m only requesting this one field in the format parameter. If I wanted more information I could simply list out the additional fields required. For example:

$containers = docker ps -a --format "{{.Names}} {{.ID}} {{.Image}}"

With my list of container names I can now loop through and invoke the Remove-NavContainer Cmdlet on each name:

$containers = docker ps -a --filter "name=c*" --format "table {{.Names}}"

foreach ($container in $containers) {
    Write-Host 'Removing ' $container
    try {
      Remove-NavContainer -containerName $container
    }
    catch {
      Write-Host 'Could not remove ' $container -f Red
    }
}

As I still had problems with the NavContainerHelper folder being locked, the script was still failing on some containers (Jenkins restart required) so I added a try-catch to make sure the script at least attempts to remove all containers.

That’s it, dirty hack temporary fix complete!