Understanding Linux Directory Structure: A Complete Guide to /bin, /etc, /usr, and More

Linux directory structure and purpose:

/bin: Binary executable commands.

/dev: Device special files.

/etc: System management and configuration files.

/etc/rc.d: Startup configuration files and scripts.

/home: User home directories (e.g., /home/user).

/lib: Standard libraries (shared objects), similar to Windows .dll files.

/sbin: System administration commands for privileged users.

/tmp: Temporary files used by programs.

/root: Home directory of the system administrator.

/mnt: Temporary mount point for other filesystems.

/lost+found: Holds orphaned files after an abnormal shutdown.

/proc: Virtual directory providing a view of system memory and information.

/var: Variable data such as logs, spools, and temporary files.

/usr: Largest directory containing most applications and files, including:

/usr/x11r6: X Window system files.

/usr/bin: General applications.

/usr/sbin: Superuser management programs.

/usr/doc: Linux documentation.

/usr/include: Header files for development.

/usr/lib: Shared libraries and package configuration.

/usr/man: Manual pages.

/usr/src: Source code (e.g., kernel source).

/usr/local/bin: Locally added commands.

/usr/local/lib: Locally added libraries.

The root filesystem should remain small, containing only essential files needed for boot and recovery; most other files reside in subdirectories.

1. /bin directory

/bin contains essential binary commands required for system boot and for regular users.

2. /sbin directory

/sbin stores binary files mainly used by system administrators; regular users can execute them only when permitted.

3. /etc directory

/etc holds various system configuration files, including user information (/etc/passwd) and initialization scripts (/etc/rc).

4. /root directory

/root is the superuser's home directory.

5. /lib directory

/lib contains shared libraries required by programs in the root filesystem, reducing duplication and saving space.

6. /lib/modules directory

/lib/modules stores loadable kernel modules, especially those needed for system recovery.

7. /dev directory

/dev contains device files that provide access to hardware (e.g., /dev/mouse).

8. /tmp directory

/tmp holds temporary data generated by programs; after boot, /var/tmp is preferred for larger temporary storage.

9. /boot directory

/boot stores bootloader files and kernel images; large numbers of kernels may warrant a separate filesystem.

10. /mnt directory

/mnt is a temporary mount point for attaching other filesystems.

11. /proc, /usr, /var, /home directories

These directories serve as major filesystem partitions, each with distinct purposes: /usr for static applications, /var for variable data, /home for user data, and /proc as a virtual interface to kernel information.

/etc filesystem

/etc includes many configuration files such as /etc/rc.d (startup scripts), /etc/passwd (user database), /etc/fstab (filesystem table), /etc/group, /etc/inittab, /etc/issue, /etc/magic, /etc/motd, /etc/mtab, /etc/shadow, /etc/login.defs, /etc/printcap, /etc/profile, /etc/securetty, /etc/shells, and /etc/termcap.

/dev filesystem

/dev provides device files like /dev/console, /dev/hd, /dev/sd, /dev/fd, /dev/st, /dev/tty, /dev/pty, /dev/ttys, /dev/cua, and /dev/null.

/usr filesystem

/usr contains most installed software and documentation, including subdirectories such as /usr/x11r6, /usr/x386, /usr/bin, /usr/sbin, /usr/man, /usr/info, /usr/doc, /usr/include, /usr/lib, and /usr/local.

/var filesystem

/var holds data that changes during system operation, including /var/catman, /var/lib, /var/local, /var/lock, /var/log, /var/run, /var/spool, and /var/tmp.

/proc filesystem

/proc is a virtual filesystem providing kernel and process information, with entries such as /proc/x, /proc/cpuinfo, /proc/devices, /proc/dma, /proc/filesystems, /proc/interrupts, /proc/ioports, /proc/kcore, /proc/kmsg, /proc/ksyms, /proc/loadavg, /proc/meminfo, /proc/modules, /proc/net, /proc/self, /proc/stat, /proc/uptime, and /proc/version.

/usr/local is typically used for manually installed software, mirroring the structure of /usr, while /opt is reserved for large third‑party applications.