Master Linux: Understanding Every Directory and Its Purpose

Linux Directory Structure Overview

/bin : Binary executable commands needed for system boot and for regular users.

/sbin : System binaries primarily used by administrators; regular users may execute them when permitted.

/etc : System configuration files, including user databases (/etc/passwd), init scripts (/etc/rc.d), and many service-specific configs.

/root : Home directory of the superuser.

/lib : Shared libraries required by programs in the root filesystem, analogous to Windows DLLs.

/lib/modules : Kernel modules needed for hardware drivers and other core functionality.

/dev : Device special files that provide access to hardware (e.g., /dev/mouse, /dev/null).

/tmp : Temporary files created by running programs; /var/tmp is preferred for larger or longer‑lived temporary data.

/boot : Files used by the boot loader, such as the kernel image and boot configuration.

/mnt : Temporary mount points for attaching other filesystems.

/proc : Virtual filesystem exposing kernel and process information (e.g., /proc/cpuinfo, /proc/meminfo, /proc/uptime).

/usr : Largest hierarchy containing most user‑level applications, libraries, manuals, and source code. Key subdirectories include:

/usr/bin – standard user commands

/usr/sbin – system administration commands

/usr/lib – shared libraries

/usr/include – C header files

/usr/share, /usr/doc, /usr/man – documentation and shared data

/usr/local – locally installed software, mirroring the /usr layout

/usr/src – source code, including the Linux kernel source

/var : Variable data that changes during system operation, such as logs (/var/log), spool directories (/var/spool), lock files (/var/lock), and temporary files (/var/tmp).

/home : User home directories where personal data and configuration reside.

The root filesystem should remain small, containing only essential files needed for boot and recovery. Larger, frequently changing directories are placed under /usr, /var, or /home to allow separate mounting and easier management.

Additional directories like /opt host large third‑party applications, while /usr/local is used for software installed manually outside the package manager.