Linux & Open Source Consulting Services

X/OS provides state-of-the-art technical consulting services related to UNIX & Linux, free & Open Source software and networking & security technologies.

About Us

About X/OS

X/OS Experts in Open Systems was founded in 1994 by UNIX experts with an academic background in computer science and a long and deep experience with systems software, including UNIX kernel development. Since the start of our company we have used Linux internally on all our systems. We joined the Linux kernel development community where we developed and maintained the firewall part of the networking stack (1995-2000). In the first years our primary business was providing technical UNIX expertise to our customers. Over time, UNIX was replaced by Linux in many environments and since then we almost exclusively work on Linux and Open Source projects.

We have given talks and courses about firewalls, software packaging and more at many conferences in Europe and the USA. We also co-organized several not-for-profit technical Linux conferences in Germany and the Netherlands, often acting as the program chair. Having personal contacts with many key people and being an active part of the community, we often can get answers to questions beyond the traditional public support channels.

Besides Linux systems software, including Internet and other networking technologies, security and firewalls, we also focus on other free and Open Source software, ranging from databases like PostgreSQL to mobile app development using state-of-the-art cross-platform tools. And last but not least, started as part of a store automation project, X/OS delivers complete point-of-sale solutions. Our strengths also include strong analytical skills, out-of-the-box thinking, and using tools (or simply writing our own) most others wouldn't even think of. Our customers range from small businesses to large banks and multinationals, and from local governments to international NGO's.

Our Expertise


We have extensive experience in network security, from developing the packet filtering and address translation code in the early Linux kernels to building customized firewall/VPN appliances, with more functionality and flexibility than off-the-shelf equipment.


For troubleshooting we often resort to analyzing network traffic and protocols. If needed, we also develop custom protocols and API's.

Internet of Things

MQTT is our preferred pub/sub protocol for connecting IoT devices, having used it for both web and mobile real-time monitoring applications.

Embedded Linux

Part of our toolbox is the know-how to embed Linux on both industrial and commodity hardware such as ARM-based routers. We have built various network appliances using minimalistic Linux distributions such as OpenWRT or stripped-down generic distributions.

Data Transformations

We are proficient in a broad brange of tools for manipulating data and can deliver any data conversion needed. This ranges from development using file formats like XML, YAML, JSON, and CVS to setting up relational database like PostgreSQL and SQLite, and using powerful layers like SQLAlchemy.

Distributions and Packaging

During the years we have done a lot of software packaging, we have built several custom distributions and we publically released our own rebuilds of the Red Hat Enterprise Linux sources.

Software Development

We develop software in many languages, from small scripts to large programs. Although we love Python, we work with many other languages, like C, C++, Perl, Bash shell, Javascript, Dart, and many more.

Mobile App Development

We use Google's Flutter platform for cross-platform mobile app development using the Dart language.

Free and Open Source Software

Our work with free software started long before X/OS was founded, so we know about the do's and don'ts in this area. This means we can judge the quality of each software package more easily and we can advise about legal aspects using or integrating this kind of software.

Open Standards

With our UNIX and Internet background, based on formal and de-facto standards like POSIX and the RFC's, we strongly believe in open standards and prefer to use them. We do not like vendor lock-ins and try to avoid these by using open standards whenever possible, preferably implemented as free and Open Source software.

Projects Implemented

A small selection of projects we have realized in the past.

Developing Firewall/VPN Applicance

As part of a larger project, we have built a custom Linux box, based on an industrial 486-based SoC-board. We used a custom stripped-down Linux distribution and implemented our ...

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Build and Install Datacenter Servers

The customer wanted a large setup of 10+ Linux-servers hosting their application using load-balancing. We sold them the custom configured and built servers, installed and configured ...

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Audit Large Linux Environment

The customer was using a large, in-house setup of Linux servers with many advanced applications (like remote desktops with streaming video, Samba as domain controller, a large ...

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Full Service Point-of-Sale

For a large chain of nearly 40 shops we implemented a complete point-of-sale solution based on Linux. Besides the POS-system itself, this includes integration of card payment terminals, ...

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A selection of the customers for which we have worked or still work.

Contact X/OS

X/OS Experts in Open Systems BV
Science Park 402
1098 XH Amsterdam
The Netherlands
You can find the location of our office on Google Maps. The office building is part of the Science Park in Amsterdam.