Explain the Linux directory structure (/etc, /var, /usr, /tmp, /home, /opt, /proc).

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The Linux filesystem follows the Filesystem Hierarchy Standard (FHS) . Key top-level directories DevOps engineers work with constantly: /etc — system-wide configuration files (e.g., /etc/nginx/nginx.conf , /etc/ssh/sshd_config , /etc/hosts ). /var — variable data: logs ( /var/log ), package state, mail spool, databases ( /var/lib/mysql ). /usr — user-installed system software: /usr/bin , /usr/lib , /usr/local for locally-compiled apps. /tmp — temporary files; typically cleared on reboot. /home — user home directories ( /home/alice ). /opt — optional / third-party software (often vendor-shipped apps). /proc — virtual filesystem exposing kernel and per-process info ( /proc/cpuinfo , /proc/meminfo , /proc/<pid> ). /sys — virtual filesystem for kernel/device info. /dev — device files (disks, terminals). /boot — kernel and bootloader. Don't list every directory — just the ones that matter for DevOps work: /etc (config), /var/log (logs), /proc (kernel info), /tmp, /home, /opt. Mention that /proc is a virtual filesystem — that detail signals real Linux experience.