FHS
also: Filesystem Hierarchy Standard
The Filesystem Hierarchy Standard (FHS) is a specification that defines the directory structure and organization of files in Linux and Unix systems, ensuring consistency across distributions.
The FHS is a standardized layout that dictates where different types of files should be located in a Linux filesystem. This allows system administrators and developers to predict where configuration files, binaries, libraries, and temporary files will be found, regardless of which Linux distribution they're using.
Key FHS directories include /bin (essential command binaries), /etc (configuration files), /home (user home directories), /var (variable data like logs), /usr (user programs and data), and /tmp (temporary files). For example, you can expect to find the ls command at /bin/ls and Apache configuration at /etc/apache2/ across most distributions.
Without the FHS, each distribution could organize files differently, making it harder to write portable scripts and transition between systems. The standard is maintained by the Linux Foundation and is followed by virtually all major Linux distributions.