System Administrator (Defence & Security)

Reaktor’s Defence & Security Unit is looking for an experienced, hands-on Lead System Administrator to join our internal IT team in Helsinki.

Our team builds and maintains secure and reliable IT environments that DefSec’s development teams depend on. The work ranges from daily maintenance and troubleshooting to automation, security, and longer-term infrastructure development.

As a Lead System Administrator, you will work hands-on as part of the team: building and maintaining systems, developing automation, and solving technical problems. Alongside your technical responsibilities, you will take ownership of the overall flow of the team’s work.

You will keep the backlog clear, bring together technical and business needs, and facilitate prioritisation together with the team and business stakeholders. In our low-hierarchy environment, your role is to help the team maintain a shared understanding of what matters most, navigate competing requirements, and move the right work forward.

• Owning, maintaining, and refining the team’s backlog to ensure clear direction and steady workflow.
• Setting priorities for upcoming work based on business impact, urgency, and technical dependencies.
• Building and maintaining DefSec’s internal IT systems.
• Developing automation for system maintenance and infrastructure management.
• Ensuring that our environments are secure, compliant, stable, and reliable.
• Troubleshooting issues across hardware, operating systems, networks, and automation.
• Working closely with developers, business stakeholders, and consultants to understand and translate their needs into actionable work.
• Improving documentation, sharing knowledge, and developing the team’s technical practices.
• Contributing to both day-to-day operations and longer-term infrastructure planning.

• At least 8 years of relevant experience in system administration or IT infrastructure.
• Proven experience in gathering requirements, prioritising a team backlog, and balancing conflicting demands.
• Demonstrated ability to work directly with business stakeholders and align technical priorities with business needs.
• Good communication skills with both technical and non-technical stakeholders.
• Strong knowledge of Linux, such as Fedora, CentOS, or similar.
• Good understanding of IP networking, VPNs, and firewalls.
• Familiarity with certificate management and authentication mechanisms.
• Hands-on scripting experience with Bash, Python, PowerShell, or similar.
• Fluency in both Finnish and English (written & spoken).
• Willingness to work primarily on-site in Helsinki.
• This position requires Finnish citizenship due to client and security regulations. The selected candidate must successfully complete a security clearance process.
• Experience with Ansible or similar automation tools.
• Familiarity with Windows and macOS desktop administration.
• Programming experience in TypeScript, Python, or Go.

For two decades, we’ve been developing qualities and capabilities for adapting, reacting, and supporting change – building Reaktor to hold up in a fast-paced environment while ensuring the well-being of our people.

While working at Reaktor, we’ll provide you with

Interested? Drop us a line – We'll be happy to hear from you!