The kernel primitives, init systems, and tooling behind the world's most-deployed OS.
Configuring unattended-upgrades (Debian/Ubuntu) and dnf-automatic (RHEL/Fedora) to apply security patches automatically, with sane limits on scope.
Combining two or more network interfaces into a single bonded interface with NetworkManager — for redundancy, throughput, or both, by mode.
Trace a modern Linux boot across firmware, boot manager, kernel, initramfs, real root, and PID 1 with safe diagnostics for each handoff.
Understand cgroup v2 hierarchy, controller delegation, CPU, memory, I/O and PID controls, using safe systemd workflows and kernel evidence.
Understand eBPF programs, verifier, maps, hooks, BTF and CO-RE, privileges and operational risks without treating kernel execution as a sandbox.
df shows free space but writes fail with ENOSPC — three distinct root causes look identical from outside; here's how to tell them apart.
Ping by IP works but hostnames don't resolve — a systematic path through resolv.conf, systemd-resolved, and nsswitch.conf finds where it breaks.
Your machine boots straight into a minimal grub rescue prompt instead of Linux. Here's how to get back to a working bootloader without reinstalling the OS.
A service won't start, logs are unhelpful, and file ownership looks correct — SELinux or AppArmor's invisible permission layer is usually why.
An application errors with EMFILE or ENFILE even though the system isn't obviously out of resources — find and raise the actual limit.