Senior System Administrator

About the role

We are looking for a Senior System Administrator on a freelance basis to support a high‑security, mission‑critical environment for a client operating at the intersection of technology and national security. You will work with advanced infrastructure used by police and intelligence services, ensuring reliability, security, and continuous improvement.

Key responsibilities

• Administer and maintain Windows and Linux server environments.
• Manage Group Policy Objects, DNS, DHCP, and Active Directory.
• Oversee, monitor, and optimise virtualised platforms such as VMware, Proxmox and Hyper‑V.
• Implement system security, patch management, backups and business‑continuity procedures.
• Design scalable, resilient architectures and evolve them over time.
• Automate repetitive tasks using Python, PowerShell, Bash, Perl or Ansible.
• Collaborate with network, security and support teams to guarantee end‑to‑end reliability.
• Diagnose and resolve complex technical issues and document infrastructure and processes.

Required profile

• Minimum 7 years of experience in Windows and Linux system administration.
• Proven expertise in virtualization, storage and security concepts.
• Strong scripting abilities (PowerShell, Bash, Python or equivalent).
• Extensive experience with Active Directory and large‑scale infrastructure migrations.
• Knowledge of cloud platforms (Azure, AWS) is a plus.
• Understanding of networking, security and identity‑management components.
• Bachelor’s or Master’s degree in IT or equivalent professional experience.
• Analytical, pragmatic, solution‑oriented and able to work under pressure.

Required skills

• Windows Server
• Linux
• Active Directory / GPO
• DNS & DHCP
• VMware, Proxmox, Hyper‑V
• Python, PowerShell, Bash, Perl, Ansible
• Azure, AWS (optional)