Windows : How to remove license key and unregister

You may require sometimes to remove the license from a Windows installation, whatever this is to re-assign a license to another machine, or before publishing an appliance, etc. Follow this procedure to put back your Windows installation to the original installation state, license wise. The following commands need to be performed with the Command Prompt… Read More »

JunOS : Upgrade return ERROR: Package signature validation failed. Aborting install.

Experiencing the following error while upgrading JunOS? Verify the signature of the new package verify-sig: cannot validate certs.pem certificate is not yet valid: /C=US/ST=CA/L=Sunnyvale/O=Juniper Networks/OU=Juniper CA/CN=PackageProductionRSA_2018/ ERROR: Package signature validation failed. Aborting install. This error could be caused by incorrect date and time set on your device (back in time). To validate the current value,… Read More »

Linux : There is no screen to be resumed matching …

Using “screen” on Linux to perform your important work? Way to go, SysAdmin 🙂 Then you might at some point encountered the following behavior – while attempting to resume a session using “screen -r”, the following message occurred : There is a screen on: (25/08/18 08:25:36 PM) (Attached) There is no screen to be… Read More »

Linux : How to get hardware serial number

The easiest way to get hardware serial and related information is using “dmidecode“. The command below should give you exactly what you need :

The command above does not usually work with “clone” computers/servers. Alternatively, you may use the command below, which will output all parts serial number availables :


Windows : Upgrade the Ubiquiti Unifi SDN Controller

This tutorial will show you the simple steps to upgrade your Ubiquiti Unifi SDN Controller running on Windows. The software can be found on the manufacturer Web site ( We recommend using the LTS (Long Term Support) version unless you need the bleeding edge features. Upgrading to newer version might not allow downgrade in case of… Read More »

Windows : How to retrieve Fiber Channel interface WWNs

Here is a simple PowerShell command that will output the FC host adapter interface WWNs.

If your interface have two ports, both will be output in order. This command have been successfully tested with QLogic adapters on Windows 2012 and 2016.

Linux : How to show domain TTL with DIG

Here is some useful commands to display a domain Time To Live (TTL) using the DIG command (which is usually included within “bind-utils” package). To display the full information :

To display the short, default answer :

NOTE : Replace “domain.tld” by the domain you want to query.

Windows : Change DNS update frequency in Active Directory

If you are not satisfied with the refresh rate of DNS within your active directory environment, there is a way of forcing it by increasing or decreasing the default setting in the registry. First of all, there is a command to find out your curent settings :

It should output something similar to :… Read More »