Marcus Wiederstein-Administrator, DevOps
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Experience
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
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
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)
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
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
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
Industry experience
See where this freelancer has spent most of their professional time.
Experienced in Information Technology, Aerospace and Defense, Banking and Finance, and Retail.
Business area experience
See which departments and functions this freelancer has contributed to most.
Experienced in Information Technology, Operations, Project Management, Business Intelligence, and 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
Education
Ruhr University Bochum
Electrical Engineering & Computer Science · Bochum, Germany
Statistics
Experience
Expertise
Profile
Frequently asked questions
Have questions? Find more information here.
Marcus is based in Dülmen, Germany and can operate in on-site, hybrid, and remote work models.
Marcus speaks the following languages: German (Native), English (Advanced).
Marcus has at least 19 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 and 1 month. Note that Marcus may not have shared all experience and actually has more experience.
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.
Marcus's most recent position is Administrator, DevOps at KZVB.
In recent years, Marcus has worked for KZVB, Decathlon mode project, MLP, Rheinmetall, and Own data center.
Marcus is most experienced in industries like Information Technology, Aerospace and Defense, and Banking and Finance. Marcus also has some experience in Retail.
Marcus is most experienced in business areas like Information Technology, Operations, and Project Management. Marcus also has some experience in Business Intelligence and Quality Assurance.
Marcus has recently worked in industries like Information Technology, Aerospace and Defense, and Banking and Finance.
Marcus has recently worked in business areas like Information Technology, Operations, and Project Management.
Marcus attended Ruhr University Bochum for Electrical Engineering & Computer Science.
The availability of Marcus needs to be confirmed.
Daily rate distribution
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Average rates for similar positions
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The average daily rate is the mean of all daily rates from recent contracts of comparable freelancers on our platform.
The median daily rate is the middle value of all daily rates — half of comparable freelancers charge less, half charge more. Unlike the average, it is barely affected by outliers.
Calculated based on our freelancers’ daily rates as of 6 Sep 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
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