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Personal Information


Mark Janssen








Dutch (native), English (fluent), German (conversational)


mark (at) sig-io (dot) nl




Mark is a mostly self-taught systems administrator with a sharp focus on Linux systems, automation and security. A strong preference for working with Open Source technology, open standards, git-versioning, text-based and command line interfaces.

With more than 20 years of professional experience with Linux system administration, and a passion for computer systems since long before.

Besides work Mark is active in various communities, as founder and board member (since 2009) of Stichting Revelation Space, a hackerspace in Den Haag and as treasurer (since 2016) of the Dutch Unix User group (Vereniging NLUUG).

Mark is also a member of RIPE and maintains his own public IPv4 and IPv6 network and hosts various non-profits and projects on this network.

As a regular visitor (and contributor) to many technical conferences he has taken the task to create audio/video-registrations (recordings and live-streams) of lectures which are published on the conference website and youtube/twitch using 100% Open Source software.


I prefer visiting tech-conferences as a good method to expand my knowledge instead of commercial training and certification tracks. I regularly attend and participate in the following conferences

  • NL Unix User Group (2x per year) (1999 – 2021)

  • Chaos Computer Conference (1999? – 2020)

  • Linux Open Administration Days (2011 – 2020)

  • Technical Dutch Open Source Event (2006 – 2018)

  • Free and Open Source Developer Europe Meeting (FOSDEM, 2000 - 2019)

And various smaller or one-off conferences, like HackerHotel, Eth0, Megabit, Berlin B-Sides, PH-Neutral, Plubmercon, Linux Kongress, SANE, WhatTheHack, Hackers At Large

Education and Certification




Red Hat Certified System Administrator — Red Hat Enterprise Linux 7


Novell Certified Linux Administrator


Sun Certified Solaris Administrator (Solaris 10)


SNIA Certified Storage Professional


ITIL Foundations


Linux Professional Institute, LPI-2 certification


HP-UX 10.X System Administration, Hewlett-Packard, Netherlands


Bachelor of Computer Science, Haagse Hogeschool, The Hague, Netherlands


Havo, Alfrink College, Zoetermeer, Netherlands


The last few years I have mostly focussed on doing systems administration and configuration using Ansible for configuration management and deployment. I have written a large collection of Ansible roles which are used in various customer environments and have created custom filters and Ansible modules.

I prefer to use Open Source and open solutions as much as possible, and release most of my own software and creations under open and free licenses.


Linux (Ubuntu, Debian, RHEL, CentOS, Rocky, Fedora) VPS platforms (Hetzner, Vultr, Digital Ocean, libvirt/kvm) Cloud Providers: Amazon-AWS, Azure,, Scaleway, Hetzner


Configuration management: Ansible Version Control: GitHub / GitLab / Git Programming and Scripting: Python, Perl, Php (entry level) Webservers and Proxies: Apache, Nginx, HAProxy, Varnish, Squid Databases: MySQL, MariaDB, PostgresQL Mail Infra: Postfix, Sendmail, Courier-mta, Spamassassin, OpenDKIM DNS: Bind9, PowerDNS


TCP/IP (v4/v6), Routing, iptables, nftables, DNS, NFS, NIS, Samba, SMTP, HTTP, common internet protocols


OpenSSH, Kerberos, SSL, TLS, X.509, Smartcard-HSM's, TOR HOTP/TOTP, Security tokens and PGP/GPG signatures and encryption

Job Experience

Jobs are listed in reverse chronological order, based on the end-date of the assignment.



Job Description


MinVWS, Den Haag

Sr system administrator for Project RDO, Realisatie Digitale Overheid. As part of a small OPS team I was responsible for daily system management, deployments of applications, troubleshooting, monitoring and tuning of the server infrastructure behind applications like BRBA, HKVI, ZKVI, and Coronacheck.

All systems are fully configured and managed by a custom Ansible stack, with applications deployed from artifacts generated by Github CI/CD workflows. My team was responsible for quickly and securily delivering application environments under very tight deadlines and following the strictest security guidelines and best-practices.

All inter-process communication used TLS/SSL encryption and many applications integrated with HSM modules. Dealing with various forms of encryption, certificates and encodings was almost a daily occurance.


EDRi, Brussel

System administrator for the EDRi (a collective of NGOs, experts, advocates and academics working to defend and advance digital rights). Responsible for maintaining (part) of their online infrastructure.


Chalet, Woerden

System administrator for Chalet Vacations, tasks include configuring and deploying systems with Ansible playbooks, tuning webserver configurations and securing the server infrastructure.


Greetz B.V. Amsterdam

Sr system administrator and IT-architect for Greetz, responsible for the network design and setup, routing, firewalls, wireless infrastructure, webservers, fileservers, batch-processing, performance tuning, monitoring and backups. Almost all of the IT-Server/Network environment used over the last 10 years has gone through my hands.

Since 2020 as a mostly remote 3rd-line support for the local team who perform the day-to-day assignments, with monitoring and 24/7 support/availability still as my responsibility.


Sig-I/O, Den Haag

Since 2009 operating Sig-I/O as sole proprietor, with some part-time consultants since 2020.


Cybersprint, Den Haag

Sr. System administrator, in charge of setting up, securing and monitoring the Cybersprint production environment using an Ansible-based deployment pipeline. All systems were fully provisioned, installed, configured and monitored using Ansible playbooks.


Vesting Finance, Hilversum

Migrating RedHat Linux systems to external cloud infrastructure, documenting and improving system-configuration using Ansible configuration-management tooling


VijfHart, Nieuwegein

Trainer for LPI and RedHat Enterprise Linux (7) courses


SpeedCast Europe, Rotterdam

Builing a mail and office infrastructure for offshore shipping, optimizing for minimal data transfer over satellite links


Logius, Den Haag

Logging and Monitoring Administrator for Logius /, building and maintaining a Logstash/ElasticSearch/Kibana stack using Ansible configuration management.


Imatica, Veenendaal

Trainer for various Linux and TCP/IP courses for Imatica /, including 5- and 10-day Linux courses and single-day TCP/IP and networking courses.

Mar/Apr 2013

Advo (nee: StepCo) Houten

Migrate existing RedHat 5 systems to RedHat Enterprise 6, setup network-backups and troubleshoot stability issues with the Microsoft Hyper-V platform used here.

Okt/Nov 2012

FloorIS Internet Services

Setting up a clustered webserver and database server environment for hosting customer websites based on Red Hat Cluster Suite, Apache, Mysql and GFSv2. Creating a backup infrastructure for all hosted systems with off-site backups using backupninja, rdiff and rsync.


Snow, Geldermalsen

As a consultant for Snow I have worked at many major multinational clients in the Telecommunications, Banking and Minerals sectors, maintaining complex Unix-centric environments


SyConOS IT, Emmeloord

As a consultant at SyConOS I was mostly consulting for the Belastingdienst, where my team managed the HP-UX systems for various departments. After this I also worked for the Network department, mostly automating switch / router deployments using perl, expect and shell-scripts


Unix Support Nederland

As a Unix consultant for Unix Support Netherlands I performed Unix System administration for various customers of USN on various Unix platforms (HP-UX, Solaris, AIX)


DelftNet Internet

After finishing my internship at DelftNet, I stayed on as a Linux Systems administrator responsible for the maintenance and configuration of the ISP's infrastructure, customer support and troubleshooting