Overriding / Patching Linux System Serial Number

I'm a big fan of test driven development (TDD) for infrastructure components. I'm currently working on a hardware-related topic where we also use the system serial number as identifier. To create a proper integration test, we need to be able to start a system and set the serial number to a known value. This can easily be done with the help of virtual machines like in VMware or VirtualBox, but I couldn't find a way for changing the system serial number on hardware boxes, cloud VMs (e.g. on Alibaba Cloud) or other Linux system.

Problem Analysis

I was thinking: Linux is the operating system where I can potentially do everything. So how hard can this be? After some digging around I found out that there are those main sources for the serial number on Linux:

  1. /sys/firmware/dmi/tables/DMI contains a binary blob of Desktop Management Interface data provided by the kernel and the dmidecode utility is commonly used to decode it and extract the system serial number like this:
  2. /sys/devices/virtual/dmi/id/product_serial and /sys/devices/virtual/dmi/id/product_uuid are text files that also contain the system serial number:

Solution Approach

The idea behind the solution presented here is to not change the serial number of the system itself, but rather change the serial number visible to software running in user space. This should be enough for most problems where software looks at the serial number to identify a system.

To solve my problem I created a little program that overrides the serial number in user space, using it looks like this:

The Code

The program can be found at override-serial-number.sh (GitHub Gist) and it looks like this:

I hope that you find it useful.

Comments

  1. James4 May 2023 at 11:50

    Thanks for this. I needed to remove VMWare from the beginning of the serial for inventory. You can't seem to do it from the VMX. This worked great.

    ReplyDelete
  2. ntks4 November 2023 at 02:50

    Thanks ,Do you have any method to override uuid?

    ReplyDelete
    Replies
    1. Schlomo4 November 2023 at 18:15

      Which UUID? Is that another file under /sys? You should be able to adapt this code for that as well.

      Delete

Post a Comment

Like this content? You could send me something from my Amazon Wishlist. Need commercial support? Contact me for Consulting Services.

Popular posts from this blog

A Login Security Architecture Without Passwords

Image
Following up on Lifting the Curse of Static Credentials and Eliminating the Password of Shared Accounts , I have many discussions about why we would benefit from removing password prompts for website logins. Let's dig deeper into the details and show why removing password prompts leads to a  safer security architecture . Update 11.03.2022: Added more details about business vs. consumer websites and additional security suggestions surrounding WebAuthn Problem Space For context, imagine a website that needs to identify online users via their email address. We assume that the website in question is not the primary email system of a user but some other website, e.g. an e-commerce shop system or a collaborative productivity tool. As a User As a user of that website I want to easily sign up for an account have an easy way to login into the account be sure that my account is protected from others or attacks be able to easily recover access to my acco...
Read more

Fixing Chrome Color Printing on Linux with HP Color LaserJet M880

Image
It seems like I can't get a printer that "just works". I recently decided to replace our HP X476 printer with something nicer and bigger, an HP Color LaserJet M880 ( background story & review in German ). And of course there is something that needs fixing: The Chrome browser on Linux wouldn't let us print in color, even though all other applications had no problem to print in color. Even with Chrome color printing was possible, if one used the system printing dialog instead of the built-in Chrome print preview. This strange behavior of course piqued my curiosity. After some digging around I found out that the Chrome browser needs to parse and understand  the printer driver PPD! Chrome tries to find out how to configure color or grayscale printing in order to offer the user the choice. If Chrome can't understand the printer driver then it simply doesn't offer the choice between color and grayscale — and then some printer driver default can ch...
Read more