ManTech International is seeking a Linux System Administrator to support mission-critical Information Technology (IT) and Technical Support operations for U.S. national security customers. In this role, you will design, implement, secure, and maintain enterprise Linux environments that underpin intelligence, defense, and federal agency systems. You will install, configure, and harden Linux servers (RHEL, CentOS, and other distributions), manage user accounts and permissions, and ensure high availability, performance, and reliability of systems across on-premises data centers and virtualized or cloud-based environments. You will monitor system health, troubleshoot complex OS, network, and storage issues, and apply patches and updates in accordance with established change management processes and security baselines. Working closely with cyber security engineers, network engineers, and software development teams, you will implement STIGs and other security controls, support vulnerability remediation, and assist in incident response to protect sensitive data and mission systems. Responsibilities also include automation of routine tasks via scripting (Bash, Python, or similar), configuration management support, backup and recovery planning and execution, log analysis, and documentation of system configurations and procedures. You will participate in on-call rotations or after-hours maintenance windows as needed to minimize operational impact. ManTech prides itself on a culture of innovation, integrity, and respect for individual contributions, and this position offers the opportunity to collaborate on cutting-edge technologies while directly supporting national security missions. ManTech offers a career path that can transition into or closely collaborate with Cyber Security Engineer roles, giving you the chance to deepen your expertise in safeguarding critical systems and contributing to the development of advanced security solutions.