Describe the Linux filesystem hierarchy and the purpose of key directories.

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The Linux filesystem follows the Filesystem Hierarchy Standard, or FHS, which defines a consistent directory structure across distributions.

The root directory, represented by a forward slash, is the top of the hierarchy. Everything else branches from here.

The /bin directory contains essential command binaries needed for single-user mode and basic system operations. Commands like ls, cp, and cat live here.

The /sbin directory holds system binaries used for administration tasks, typically requiring root privileges. Commands like fdisk, iptables, and reboot are found here.

The /etc directory stores system-wide configuration files. Network settings, user information, and service configurations all live in /etc. For example, /etc/passwd contains user account information.

The /home directory contains personal directories for each user. A user named alice would have /home/alice as her home directory, storing personal files and user-specific configurations.

The /var directory holds variable data that changes during operation. Log files go in /var/log. Mail spools, print queues, and temporary files also reside under /var.

The /tmp directory provides temporary file storage that is typically cleared on reboot. Applications use this for files they do not need to persist.

The /usr directory contains user programs and data that is read-only after installation. /usr/bin has user command binaries. /usr/lib contains libraries. /usr/share has architecture-independent data like documentation.

The /opt directory is for optional third-party software packages that are not part of the default installation.

The /dev directory contains device files representing hardware components. For example, /dev/sda represents the first hard drive.

The /proc directory is a virtual filesystem providing information about running processes and system information. Files here are generated dynamically by the kernel.

The /mnt and /media directories are mount points for temporary and removable filesystems like USB drives or network shares.