Use PowerShell DSC

Estimated reading time: 4 minutes

Windows PowerShell Desired State Configuration (DSC) is a configuration management tool that extends the existing functionality of Windows PowerShell. DSC uses a declarative syntax to define the state in which a target should be configured. More information about PowerShell DSC can be found at http://technet.microsoft.com/en-us/library/dn249912.aspx.

Requirements

To use this guide you need a Windows host with PowerShell v4.0 or newer.

The included DSC configuration script also uses the official PPA so only an Ubuntu target is supported. The Ubuntu target must already have the required OMI Server and PowerShell DSC for Linux providers installed. More information can be found at https://github.com/MSFTOSSMgmt/WPSDSCLinux. The source repository listed below also includes PowerShell DSC for Linux installation and init scripts along with more detailed installation information.

Installation

The DSC configuration example source is available in the following repository: https://github.com/anweiss/DockerClientDSC. It can be cloned with:

$ git clone https://github.com/anweiss/DockerClientDSC.git

Usage

The DSC configuration utilizes a set of shell scripts to determine whether or not the specified Docker components are configured on the target node(s). The source repository also includes a script (RunDockerClientConfig.ps1) that can be used to establish the required CIM session(s) and execute the Set-DscConfiguration cmdlet.

More detailed usage information can be found at https://github.com/anweiss/DockerClientDSC.

Install Docker

The Docker installation configuration is equivalent to running:

apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys\
36A1D7869245C8950F966E92D8576A8BA88D21E9
sh -c "echo deb https://apt.dockerproject.org/repo ubuntu-trusty main\
> /etc/apt/sources.list.d/docker.list"
apt-get update
apt-get install docker-engine

Ensure that your current working directory is set to the DockerClientDSC source and load the DockerClient configuration into the current PowerShell session

. .\DockerClient.ps1

Generate the required DSC configuration .mof file for the targeted node

DockerClient -Hostname "myhost"

A sample DSC configuration data file has also been included and can be modified and used in conjunction with or in place of the Hostname parameter:

DockerClient -ConfigurationData .\DockerConfigData.psd1

Start the configuration application process on the targeted node

.\RunDockerClientConfig.ps1 -Hostname "myhost"

The RunDockerClientConfig.ps1 script can also parse a DSC configuration data file and execute configurations against multiple nodes as such:

.\RunDockerClientConfig.ps1 -ConfigurationData .\DockerConfigData.psd1

Images

Image configuration is equivalent to running: docker pull [image] or docker image rm -f [IMAGE].

Using the same steps defined above, execute DockerClient with the Image parameter and apply the configuration:

DockerClient -Hostname "myhost" -Image "node"
.\RunDockerClientConfig.ps1 -Hostname "myhost"

You can also configure the host to pull multiple images:

DockerClient -Hostname "myhost" -Image "node","mongo"
.\RunDockerClientConfig.ps1 -Hostname "myhost"

To remove images, use a hashtable as follows:

DockerClient -Hostname "myhost" -Image @{Name="node"; Remove=$true}
.\RunDockerClientConfig.ps1 -Hostname $hostname

Containers

Container configuration is equivalent to running:

docker run -d --name="[containername]" -p '[port]' -e '[env]' --link '[link]'\
'[image]' '[command]'

or

docker container rm -f [containername]

To create or remove containers, you can use the Container parameter with one or more hashtables. The hashtable(s) passed to this parameter can have the following properties:

  • Name (required)
  • Image (required unless Remove property is set to $true)
  • Port
  • Env
  • Link
  • Command
  • Remove

For example, create a hashtable with the settings for your container:

$webContainer = @{Name="web"; Image="anweiss/docker-platynem"; Port="80:80"}

Then, using the same steps defined above, execute DockerClient with the -Image and -Container parameters:

DockerClient -Hostname "myhost" -Image node -Container $webContainer
.\RunDockerClientConfig.ps1 -Hostname "myhost"

Existing containers can also be removed as follows:

$containerToRemove = @{Name="web"; Remove=$true}
DockerClient -Hostname "myhost" -Container $containerToRemove
.\RunDockerClientConfig.ps1 -Hostname "myhost"

Here is a hashtable with all of the properties that can be used to create a container:

$containerProps = @{Name="web"; Image="node:latest"; Port="80:80"; `
Env="PORT=80"; Link="db:db"; Command="grunt"}
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