Marcus Wiederstein - Administrator, DevOps

Q: Where is Marcus based?

Marcus is based in Dülmen, Germany and can operate in on-site , hybrid , and remote work models.

Q: What languages does Marcus speak?

Marcus speaks the following languages: German (Native), English (Advanced) .

Q: How many years of experience does Marcus have?

Marcus has at least 18 years of experience. During this time, Marcus has worked in at least 6 different roles and for 6 different companies . The average length of individual experience is 3 years . Note that Marcus may not have shared all experience and actually has more experience.

Q: What is Marcus's latest experience?

Marcus's most recent position is Administrator, DevOps at KZVB .

Q: What companies has Marcus worked for in recent years?

In recent years, Marcus has worked for KZVB , Decathlon mode project , MLP , Univention Corporate Server project , and Rheinmetall .

Q: Which industries is Marcus most experienced in?

Marcus is most experienced in industries like Information Technology (IT) , Aerospace and Defense , and Banking and Finance . Marcus also has some experience in Retail .

Q: Which business areas is Marcus most experienced in?

Marcus is most experienced in business areas like Information Technology (IT) , Operations , and Project Management . Marcus also has some experience in Business Intelligence and Quality Assurance (QA) .

Q: Which industries has Marcus worked in recently?

Marcus has recently worked in industries like Information Technology (IT) , Aerospace and Defense , and Banking and Finance .

Q: Which business areas has Marcus worked in recently?

Marcus has recently worked in business areas like Information Technology (IT) , Operations , and Project Management .

Recommended expert

Dülmen, Germany

Experience

Oct 2024 - Jul 2025

10 months

Administrator, DevOps

KZVB

Planned and implemented new network infrastructure (VLAN, LACP, DMZ, structured cabling)
Migrated from VMware to KVM using Oracle Linux Virtualization Manager (OLVM), including CPU pinning
Hardened the entire environment using SELinux (KVM hosts, container hosts, database servers)
Configured and operated the virtualization platform with OLVM and Ansible-based provisioning
Containerized and redeployed critical services: WordPress, Jenkins, PostgreSQL, MariaDB, Subversion with Apache + AD integration
Developed Ansible playbooks for automated deployment and configuration management
Integrated Foreman for repository and security management in the DMZ
Produced technical documentation in Markdown; organized in Bookstack
Coordinated with external vendors (e.g. HPE) for hardware installation and setup
Delivered all contributions documented and reproducible in Markdown

Jul 2023 - Oct 2024

1 year 4 months

DevOps Engineer / IT Consultant / System Administrator

Decathlon mode project

Operated and improved a complex production environment (Ansible, Docker, Kubernetes, Git)
Administered PostgreSQL and Oracle database instances
Analyzed and maintained virtualization and storage infrastructure (vSphere, HPE 3PAR, Multipath)
Delivered onboarding and technical training for internal administrators (Ansible, Kubernetes, CI/CD)
Created technical documentation and ensured knowledge transfer
Integrated Linux servers with Active Directory domain using SSSD
Maintained Docker container environments and KVM-based virtual machines
Refactored and extended Bash and Python scripts
Corrected and enhanced existing Ansible playbooks
Conducted workshops and introduced ChatGPT/Gemini for prompt engineering

Feb 2021 - Oct 2023

2 years 9 months

DevOps Engineer / Linux Specialist / Database Migration

MLP

Supported design and operation of Kubernetes clusters (deployment, Helm, monitoring)
Managed containerized applications (logging, secrets, persistent volumes, registry integration)
Migrated live Oracle databases to PostgreSQL using Altova MapForce, Python, and pgloader
Set up a highly available PostgreSQL environment with streaming replication and VIP failover
Developed automation scripts for data migration and verification (Python, Bash)
Administered mixed Linux platforms (SLES, Ubuntu, RHEL)

Dec 2019 - Jul 2021

1 year 8 months

DevOps, Linux Administrator

Univention Corporate Server project

Designed and implemented a Samba-compatible Active Directory domain with Univention Corporate Server
Integrated UCS into existing Linux and Windows environments
Developed automation scripts in Python for user provisioning, ACLs, and backups
Documented the domain architecture and created handover procedures
Provided consulting on LDAP/Kerberos-based application integration

Jun 2017 - Dec 2021

4 years 7 months

Administrator, XSD Designer, Data Analyst

Rheinmetall

Designed and documented complex XML/XSD target structures
Created reusable and configurable mapping templates in Altova MapForce
Implemented multi-stage mappings: Oracle → XML → JSON
Automated mapping processes via MapForce scripts and job scheduling
Integrated schema validation and test datasets
Optimized performance for large data volumes and repeated runs

Jan 2008 - Present

18 years 2 months

IT Project Manager, System Administrator

Own data center

Planned, set up, and operated a fully self-hosted data center with fibre uplink and static IPs
Virtualized using KVM (virsh) and Ceph block storage with multipath connectivity
Deployed and operated a Kubernetes platform for containerized services
Dockerized core services: Bookstack, Nextcloud, OpenProject, Mailcow
Built firewall and VPN infrastructure with OPNsense and WireGuard
Integrated Samba-based Active Directory domain with Kerberos and SSSD for Linux systems
Implemented browser-based training system via Apache Guacamole (snapshots, file transfer)
Rebuilt and migrated company websites with WordPress into private infrastructure
Used AI tools (ChatGPT/Gemini) for documentation, automation, and operational support
Maintained stable, high-performance infrastructure with 24/7 availability
Created scalable training platform with isolated, resettable DevOps/Kubernetes/Linux labs

Industries Experience

See where this freelancer has spent most of their professional time. Longer bars indicate deeper hands-on experience, while shorter ones reflect targeted or project-based work.

Experienced in Information Technology (18 years), Aerospace and Defense (4.5 years), Banking and Finance (2.5 years), and Retail (1.5 years).

Information Technology

Aerospace and Defense

Banking and Finance

Retail

Business Areas Experience

The graph below provides a cumulative view of the freelancer's experience across multiple business areas, calculated from completed and active engagements. It highlights the areas where the freelancer has most frequently contributed to planning, execution, and delivery of business outcomes.

Experienced in Information Technology (18 years), Operations (18 years), Project Management (18 years), Business Intelligence (4.5 years), and Quality Assurance (4.5 years).

Information Technology

Operations

Project Management

Business Intelligence

Quality Assurance

Summary

I support companies in building digital infrastructures that are self-determined, maintainable, and future-proof – based entirely on open-source technologies and independent of proprietary ecosystems. I place strong emphasis on knowledge transfer through structured documentation and hands-on training.

I take a holistic view of IT – from the network layer to container platforms to stable applications.

For refining language, exploring edge cases, and reflecting on architectural choices, I occasionally use supportive tools like ChatGPT and Gemini – for structure, phrasing, best-practice input, and sometimes a bit of emotional support during long working phases. All decisions, content, and technical solutions, however, are based entirely on my own expertise and experience.

Skills

Linux Administration: Debian, Ubuntu, Rhel, Oracle Linux; Systemd, Lvm, Crontab, Shell, Ssh, Journalctl
Infrastructure, Networking & Security: Vlan, Trunking, Fibre Channel, Lacp, Multipath, Ceph (Block Storage)
Firewall/vpn: Opnsense, Flexiwan, Openwrt, Wireguard
Security: Selinux, Apparmor, Clamav, Rspamd, Tls Certificates, Ssh Hardening, Network Hardening, Kerberos, Openscap
Ldap/authentication: Samba Ad, Sssd, Pam, Winbind, Kerberos, Apache Modules (Mod Authnz Ldap, Mod Auth Kerb)
Openstack (Core Services): Nova, Neutron, Keystone, Ceph, Cinder (Ceph Backend), Horizon
Monitoring: Prometheus, Grafana, Snmp-based Hardware Monitoring
Hardware/hosting: Raspberry Pi, Disk Enclosures, Fibre Channel, Self-hosting Setups
Virtualization: Proxmox Ve, Kvm With Virsh, Oracle Linux Virtualization Manager (Olvm)
Kubernetes: Kubespray (Provisioning With Ansible), Cluster Setup, Deployment, Helm, Kustomize, Gitops, Opa/gatekeeper, Secrets, Volumes, Rbac, Kubevirt, Longhorn
Containerization: Docker, Docker Compose
Openstack (Integration): Ansible, Heat (Orchestration), Magnum (Kubernetes On Openstack), Automation
Automation & Scripting: Ansible, Bash, Git, Python, Php
Databases (Postgresql): Administration, Security, High Availability, Performance Tuning, Monitoring, Ci/cd, Migration, Operation On Docker, Kubernetes And On-premise, Backup & Recovery (Including Pitr), Clustering, Replication
Databases (Mariadb/mysql): Security, Monitoring, Ci/cd Integration, Docker/kubernetes Integration, Performance Tuning
Migration & Mapping: Altova Mapforce, Talend Open Studio
Server Software: Apache2, Nginx, Mailcow, Wordpress, Ha Cluster, Apache Guacamole, Samba
Self-hosted Tools: Bookstack, Nextcloud, Opentalk, Openproject, Git, Freeswitch, Espro Crm, Matrix/element
Diy And Infrastructure Projects: Raspberry Pi-based Home Servers, Network Test Environments, Backup Servers
Training & Lab Environments: Virtual Lab Setups With Kvm, Browser-based Access Via Apache Guacamole, Use Of Ansible, Kubernetes And Git
Ai & Documentation: Chatgpt/gemini Prompt Engineering, Markdown-based Workflows, Bookstack Knowledge Systems

Languages

German

Native

English

Advanced

Education

Ruhr University Bochum

Electrical Engineering & Computer Science · Bochum, Germany

Profile

Created

August 2025

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Frequently asked questions

Do you have questions? Here you can find further information.

Where is Marcus based?

Marcus is based in Dülmen, Germany and can operate in on-site, hybrid, and remote work models.

What languages does Marcus speak?

Marcus speaks the following languages: German (Native), English (Advanced).

How many years of experience does Marcus have?

Marcus has at least 18 years of experience. During this time, Marcus has worked in at least 6 different roles and for 6 different companies. The average length of individual experience is 3 years. Note that Marcus may not have shared all experience and actually has more experience.

What roles would Marcus be best suited for?

Based on recent experience, Marcus would be well-suited for roles such as: Administrator, DevOps, DevOps Engineer / IT Consultant / System Administrator, DevOps Engineer / Linux Specialist / Database Migration.

What is Marcus's latest experience?

Marcus's most recent position is Administrator, DevOps at KZVB.

What companies has Marcus worked for in recent years?

In recent years, Marcus has worked for KZVB, Decathlon mode project, MLP, Univention Corporate Server project, and Rheinmetall.

Which industries is Marcus most experienced in?

Marcus is most experienced in industries like Information Technology (IT), Aerospace and Defense, and Banking and Finance. Marcus also has some experience in Retail.

Which business areas is Marcus most experienced in?

Marcus is most experienced in business areas like Information Technology (IT), Operations, and Project Management. Marcus also has some experience in Business Intelligence and Quality Assurance (QA).

Which industries has Marcus worked in recently?

Marcus has recently worked in industries like Information Technology (IT), Aerospace and Defense, and Banking and Finance.

Which business areas has Marcus worked in recently?

Marcus has recently worked in business areas like Information Technology (IT), Operations, and Project Management.

What is Marcus's education?

Marcus attended Ruhr University Bochum for Electrical Engineering & Computer Science.

What is the availability of Marcus?

Marcus is immediately available full-time for suitable projects.

What is the rate of Marcus?

Marcus's rate depends on the specific project requirements. Please use the Meet button on the profile to schedule a meeting and discuss the details.