Sr. Linux Systems Administrator

Astrion has an exciting opportunity for a highly experienced Senior Linux Systems Administrator to build, secure, and sustain the Linux server and workstation estate, the high-performance computing (HPC) cluster, and the enterprise storage that run across three or more isolated classified networks supporting Department of Defense/Department of War (DoD/DoW) environments in Columbia, MD. The ideal candidate brings deep Red Hat Enterprise Linux (RHEL) expertise, extensive experience operating inside closed and air-gapped classified enclaves, and a proven record of building and maintaining systems in compliance with Risk Management Framework (RMF), DoD STIG, and Comply-to-Connect (C2C) requirements. This position requires Monday through Friday on-site work at our facility in Columbia, MD., * Administer, patch, and sustain RHEL servers and workstations across three or more isolated classified networks, each operated as its own authorization boundary

• Build, harden, and baseline Linux systems to DoD Security Technical Implementation Guides (STIGs); remediate findings and control configuration drift
• Administer and tune the HPC cluster, including compute nodes, the workload scheduler (e.g., PBS Professional), the shared or parallel filesystem, and the low-latency interconnect
• Administer NetApp storage (ONTAP), including volumes, NFS and CIFS exports, snapshots, capacity planning, and backup and recovery
• Automate provisioning, configuration, and remediation with Bash, Python, and Ansible, including on disconnected systems
• Perform patching and updates on air-gapped networks through approved offline processes (e.g., Red Hat Satellite or internal repositories and trusted media transfer)
• Administer Linux identity and access (LDAP/SSSD, Kerberos, FreeIPA or Active Directory integration, sudo, PAM), enforcing least privilege
• Implement and maintain C2C and 802.1x posture for Linux endpoints and integrate with the security tool stack
• Perform vulnerability remediation and continuous monitoring in accordance with RMF controls; run and interpret ACAS and SCAP scans and review audit logs
• Support the Authority to Operate (ATO) process, including STIG checklists, POA&Ms, and risk assessments
• Develop and maintain system documentation, diagrams, SOPs, and security artifacts
• Troubleshoot complex issues across multi-network, multi-vendor environments
• Collaborate with cybersecurity, network, systems engineering, and mission stakeholders to ensure secure, reliable operations
• Support audits, inspections, and compliance validation activities

• Active TS/SCI security clearance (required)
• Bachelor’s degree in Computer Science, Information Technology, or related field (or equivalent experience)
• 8+ years of Linux systems administration experience within DoD/DoW or classified environments
• Deep expertise in:
• RHEL administration (installation, patching, performance tuning, kernel and systemd, storage, and networking)
• Scripting and automation (Bash, Python, Ansible)
• Linux identity and authentication (LDAP/SSSD, Kerberos, FreeIPA or AD integration)
• Demonstrated experience implementing and maintaining DoD STIG compliance on Linux
• Hands-on experience administering an HPC cluster (workload scheduler such as PBS Professional or similar)
• Experience administering enterprise storage (NetApp ONTAP, NFS)
• Strong understanding of:
• RMF (Risk Management Framework)
• DISA security requirements and accreditation processes
• DCSA accreditation standards
• Active DoD 8140 (formerly DoD 8570) compliant baseline certification (e.g., Security+ CE, CISSP)
• Active DoD 8140 compliant computing environment certification (e.g., minimum Red Hat Certified System Administrator (RHCSA))
• Experience with:
• Offline and air-gapped patching (Red Hat Satellite or internal repositories)
• ACAS or Nessus and SCAP scanning
• SIEM integration and log analysis
• Continuous monitoring under RMF

KEY COMPETENCIES

• Advanced Linux systems administration and troubleshooting
• Security hardening and compliance enforcement
• Automation and scripting
• Strong analytical and problem-solving abilities
• Excellent communication and documentation skills
• Ability to operate in high-security, mission-critical environments, * Red Hat Certified Engineer (RHCE) or Red Hat Certified Architect (RHCA)
• HPC experience with PBS Professional
• NetApp Certified Data Administrator (NCDA)
• Automation at scale (Ansible Automation Platform, Git-based configuration management)
• Zero Trust architectures and containerization (Podman, Kubernetes) in classified environments
• Prior experience supporting Cross Domain Solutions (CDS) programs
• Experience with cloud-based DoD environments (e.g., Azure Government, Azure Secret)
• Project management experience and experience briefing executive leadership