Linux System Administration Questions

Linux specific system administration and deep operating system topics. Areas include Linux kernel concepts, process lifecycle and signals, memory management and swap behavior in Linux, Linux file systems and permission models, boot processes and init systems such as systemd, package management and software installation, service management and system daemons, shell and scripting for automation and debugging, performance tuning and profiling, log management and diagnostic techniques, security and access control on Linux, and approaches to investigating and resolving systemic failures in Linux environments. At senior levels candidates should demonstrate both operational competence and an understanding of internal mechanisms and trade offs.

MediumTechnical

24 practiced

A service does not respond to systemctl stop and continues running. Explain how Linux signals (SIGTERM, SIGINT, SIGKILL) are delivered, how a process may ignore or trap signals, and how systemd's KillSignal and KillMode settings affect behavior. Describe step-by-step how you would debug and fix this (using ps, pstree, strace, gdb if needed).

HardTechnical

22 practiced

Explain the Linux Completely Fair Scheduler (CFS): vruntime, how the scheduler balances runqueues across CPUs, and how load_avg affects scheduling. For a latency-sensitive real-time service, discuss tuning options (isolcpus, cpuset, SCHED_FIFO) and the trade-offs that come with using real-time priorities.

MediumTechnical

19 practiced

Configure auditd rules to log all sudo executions and failed SSH login attempts with minimal performance impact. Provide sample auditctl or /etc/audit/rules.d rules and explain how to query these entries using ausearch or aureport and how to correlate with journalctl.

MediumTechnical

21 practiced

Explain vm.swappiness, vm.dirty_ratio, vm.dirty_background_ratio and how they affect writeback and latency. Provide example sysctl settings you might apply for a write-heavy database host and explain the trade-offs of reducing dirty ratios.

MediumTechnical

16 practiced

A binary deployed fleet-wide starts crashing with SIGSEGV after a glibc update. Outline steps to reproduce locally, collect core dumps in systemd environments (systemd-coredump or ulimit), analyze a core with gdb and addr2line, determine whether to rollback glibc or patch the binary, and how to stage a rollback safely.

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