Tips & Tricks

PrtgDocker enables sysadmins that may not have any experience with Docker to containerize their PRTG systems without necessarily having to worry about understanding the basics of the Docker CLI. A side effect of this however is that a. when something goes wrong, you have no idea what to do, which ties in with b. Docker for Windows has a lot of problems that don't exist on other platforms (which ties in with the above)

Migrating to Docker Probes

Because Docker Probes are not technically part of your domain, a number of challenges can present themselves when moving your existing infrastructure over from a physical probe to a containerized probe. The following is a list of challenges you may encounter, and how you can work around them

Adding Custom Sensors

DNS Resolution

Custom Script Security Contexts

EXE/XML Advanced custom sensors have the option of running in the security context of the PRTG Probe service, or the Windows account defined on the device. As containerized probes are not on the domain however, you will get an access denied error from PRTG when it attempts to run your script.

To work around this, you can change all of the affected sensors to use the security context of the probe service. You can easily do this for multiple sensors by using PrtgAPI.

Get-Probe "New York 1" | Get-Sensor -Type exexml | Set-ObjectProperty -UseWindowsAuthentication $false

You will then need to modify your script to specify your credentials explicitly.

You can either do this in clear text

function New-Credential
{
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [string]
        $UserName,

        [string]
        $Password
    )

    $secureString = ConvertTo-SecureString $Password -AsPlainText -Force

    New-Object System.Management.Automation.PSCredential -ArgumentList $UserName, $secureString
}

$cred = New-Credential username password

Invoke-Command -ComputerName $server {
    ...
} -Credential $cred

Or with some level of obfuscation

$encryptedPassword = "76492d1116743f0423413b16050a5345MgB8..."
$key = 54,60,18,60,10,20...
$password = ConvertTo-SecureString $encryptedPassword -Key $key
$cred = New-Object PSCredential -ArgumentList @("username", $password)

Invoke-Command -ComputerName $server {
    ...
} -Credential $cred

Restart Policy

By default PrtgDocker sets the restart policy of PRTG docker containers to --restart always. This has been confirmed to work on both Server 2016 and Server 2019. In some cases however the policy will fail to work if you've installed something on your system that messed with the default networking (potentially Hyper-V?). In this case you will need to either identify and resolve the direct cause of the issue, configure automatic startup for your containers via the use of a Scheduled Task that executes a startup script (docker start <name>) or build a new server that does not have this issue

Common Commands

While PrtgDocker makes it easy to create PRTG images and containers without requiring any existing Docker CLI knowledge, once the images have been deployed you're on your own to manage your containers.

The following lists some common commands that you should be aware of when attempting to use Docker

Images

• docker image ls: List all images on your system
• docker rm <repoAndTagOrId>: Removes the container with the specified repository and tag or ID

Containers

• docker container ls: List all running containers on your system
• docker container ls -a: List all containers on your system
• docker start <nameOrId>: Starts the container with the specified name or ID
• docker stop <nameOrId>: Stops the container with the specified name or ID
• docker rm <nameOrId>: Removes the container with the specified name or ID
• docker <command> (docker container ls -q): Performs a command for all running containers on your system
• docker <command> (docker container ls -qa): Performs a command for all containers on your system
• docker inspect <nameOrId>: inspects the configuration of the container with the specified name or ID

Troubleshooting

• docker exec -it <nameOrId> powershell: Opens a PowerShell prompt inside of a running container with a specified name or ID