WilliamLam.com

How do you "log a reason" using PowerCLI when rebooting or shutting down ESXi host?

by // 2 Comments

I am sure many of you have seen this UI prompt asking you to specify a reason before issuing a reboot or shutdown of an ESXi host and I assume most of you spend a few seconds to type in a useful message and not just random characters, right? 😉


Have you ever tried performing the same reboot or shutdown operation using the vSphere API or PowerCLI (which leverages the API)? Have noticed, there is not a way to specify a message like you can in the UI?

Here is a table of the PowerCLI cmdlets and the respective vSphere API that is used to perform these two operations:

Operation Cmdlet vSphere API
Reboot  Restart-VMHost  RebootHost_Task
Shutdown  Stop-VMHost  ShutdownHost_Task

When looking at either the PowerCLI and/or vSphere API documentation, we can confirm that there are no fields to specify a message which can lead to an assumption that this is simply not possible or that the functionality might be provided by a private API. Fortunately, this is not the case and the functionality is in fact in the public vSphere API and has been for quite some time.

When you specify a message prior to rebooting or shutting down, this message is actually persisted and implemented as an Event within vCenter Server as shown in the screenshot below.

Instead of being able to specify a message that is only applicable to an ESXi host, I believe the original vSphere API designers thought that this functionality could also be useful and applied more broadly across any number of the vSphere Inventory objects, not just ESXi hosts. As such, this functionality which the vSphere UI uses is provided by the LogUserEvent() method which is part of the EventManager API. Customers or solutions can leverage this mechanism to log custom user defined events which is then persisted with the lifecycle fo the vSphere Inventory Object or as far back as your retention period for vCenter Server Events.

Going back to our original question, if you want to specify a message prior to rebooting or shutting down an ESXi host, the following snippet below demonstrates the use of the vSphere API via PowerCLI:

$eventManager = Get-View eventManager
$vmhost = Get-VMHost -Name 192.168.30.11
$message = "This message will be logged"

$eventManager.LogUserEvent($vmhost.ExtensionData.MoRef,$message)

Quick Tip - What hashing algorithm is supported for ESXi Kickstart password?

by // 2 Comments

I had a question the other day asking whether the encrypted password which can be specified within an ESXi Kickstart file (denoted by the --isencrypted flag) can use a different hashing algorithm other than MD5? The answer is absolutely yes. In fact, MD5 as a default hashing algorithm has NOT been used for a number of releases, probably dating back to classic ESX (you know, the version that had the Service Console).

For all recent releases of ESXi including 5.5 to 6.7, the default hashing algorithm has been SHA512 for quite some time now. Below are two ways in which you can check which default hashing algorithm is currently being used:

Option 1 - SSH to ESXi host and take a look at /etc/pam.d/passwd


Option 2 - SSH to ESXi host and take a look at /etc/shadow and look at the field prior to the salt.

As a reference:

  • $1$ - MD5
  • $5$ - SHA256
  • $6$ - SHA512

New VMware Configuration Maximum Tool

by // 1 Comment

VMware has just released a new web-based tool that will enable customers to easily view and compare product configuration maximums across different VMware product versions. You can access the easy to remember URL by going to: https://configmax.vmware.com

In this first release of this tool, customers will have the ability to look up configuration maximums for vSphere (includes VSAN) which will initially support vSphere 6.0, vSphere 6.5, vSphere 6.5 Update 1 & the recently released vSphere 6.7 as well as comparing across versions. To view the existing vSphere configuration maximum, simply click on the "Get Started" button.


As you can see from the screenshot below, you now have a single place where you can view the vSphere configuration maximums across different versions. Once you have selected the target version, you can either view all maximums or you can selectively choose the sections you are interested in.


The other really neat feature is the ability to compare the configuration maximums across different vSphere versions. This is really useful for customers to be able to quickly tell what improvements and enhancements have been made, especially as customers plan for vSphere upgrades. To begin, simply click on the "Compare Limits" button at the top. Next, select  the target vSphere version and then you can add one or more versions to compare against.


Once you click on the Compare button, a new window will popup providing you the comparison between the target and selected vSphere versions. You can quickly see how the maximums have changed across these vSphere versions. You can even export the results to Excel by click on export option on the upper right hand corner and you be prompted to save a CSV file.


I can tell you, this definitely beats having to manually Google for the correct vSphere configuration maximum document since I can never remember the long URL to the static PDF documents! I am excited to see the improved user experience when consuming our product maximums and I know the team will be working on adding more products and features in the future. Definitely keep an eye on this site and also be sure to update your bookmarks. If you have any feedback or things you would like to see, feel free to leave a comment and I will make sure it reaches the Product and Development teams.