Debian follows the Filesystem Hierarchy Standard (FHS), a standard layout for Linux filesystems. Understanding the directory structure helps you find files, configure systems, and write portable scripts.
Key directories:
/bin, /usr/bin: executable programs (built-in commands and utilities)/sbin, /usr/sbin: system programs (usually require root)/lib, /usr/lib: libraries and shared objects/etc: system configuration files (editable)/home: user home directories (e.g., /home/alice/)/root: root user's home directory/tmp: temporary files (cleared on reboot)/var: variable data: logs (/var/log), cache (/var/cache), databases/opt: optional third-party software/usr/share: documentation, data files, locale files/usr/local: locally compiled software (doesn't get overwritten by package updates)$ ls / # list root directories $ df -h # show disk usage by filesystem $ mount # show mounted filesystems $ du -sh /var/log # disk usage of a directory
Tip: Configuration files in /etc usually have .dist backups. Always back up /etc before making changes—it's your system's personality.