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Showing posts from 2020

Send Syslog Messages from PowerShell

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In most cases, the scripts, functions and cmdlets we develop have to save events to a log file to make troubleshooting easier. With PowerShell, the easiest thing would be to write an event to the event log or a file.

When it comes to centralized log management, most organizations have based their strategy on the syslog server and protocol. There may be agents on the windows server machines that your code is running on to collect the messsages but that's not always the case.

So how can we send messages to a syslog server directly using PowerShell? Although that's not that hard, I've put together a cmdlet to do just that!

My General PowerShell module that is published on the Gallery contains the  Send-SyslogMessage cmdlet from version 2.12.0 onwards.

A call to the Send-SyslogMessage would be pretty much like the following:

Send-SyslogMessage -Server syslog.lab.local `-Severity Error `-Facility Local0 `-Message "An error occured."`-Application "MyScript"`-P…

Office 365 Endpoint IP Address and URL Service

In the era of the cloud, service releases and changes are nearly constant. Microsoft Office 365 could not be an exception, especially with the large and increasing number of services and millions of users.
But some of those changes and releases sometimes cause issues with on-premises infrastructure that is not property configured. Today I am going to focus on the networking side of things and talk about allowing access to Office 365 services from firewall and proxy servers.
The first thing you'll need to permit access to Office 365 services from your on-premises machines is to know the service endpoints and by endpoints I mean IP addresses and URLs. Fortunatelly, this information is available from Microsoft in this  article so the only thing you'll have to do is read through it, get the information for the services you're using and configure your proxy server and firewall.
That's easy, what happens though when that information is updated? This is where the problems start.…

Active Directory Domain Join Delegation

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The trigger to write this article was a troubleshooting session with a client that had built an automation process to deploy Windows Server and RedHat Enterprise Linux virtual machines on Azure. One of the steps of the provisioning process was to join the machine to the IaaS Active Directory Domain that was deployed on Azure and for this, an Active Directory account was required.

Following the least previlege principle, the account used in the automation processes to join machines to the domain was a plain account that could indeed perform this operation. After some successfull joins however, the process started encountering errors when trying to join machines to the domain.

As it turns out, the architects and security engineers had missed the fact that plain Active Directory accounts have the ability to only join a specific number of machines to the domain. When the automation reached that number, the process started to fail.

To further troubleshoot the issue, we tried to join the ma…

Azure Instance Metadata Service

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The Azure Instance Metadata service is an Azure service that provides more information about Azure Virtual Machines that is invoked from the machine itself. This way, the administrators of the machine - that in most cases have no access to the Azure Portal - are able to get more information and troubleshoot potential issues.

Let's use a linux virtual machine to get information from the metadata service!

To get the data from the service, a simple HTTP call is all that is required. However, there are a couple of things to keep in mind.

First, although we are using Automatic Private IP Addressing, we have to include the "Metadata" header so that the service won't mistake our call for a call that may be the result of a redirection.

Second, the version of the API to use must be provided in every request. To get the allowed values, simply call the service without the "api-version" parameter and it should return a list of values:

curl -H Metadata:true "http://…