linux/Filesystem Hierarchy (FHS) at main · jahidislam1204/linux · GitHub

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1. bin

/bin --->> binary
which contains all the essential command system binary executables
required for the system to function properly.

2. boot

contains all the essential files needed for the boot properly
Includes Linux kernel, the GRUB bootloader, and other startup files.

Important Files in /boot
vmlinuz – The compressed Linux kernel.
initrd.img – The initial RAM disk, used to load necessary drivers during boot.
grub/ – Contains GRUB bootloader files and configuration.
System.map – A symbol lookup table for debugging the kernel.


3. etc

 a critical system folder that stores configuration files for the system and installed applications.
 control system behavior, services, networking, and user access.

/etc/passwd	         Stores user account information.
/etc/shadow	         Stores encrypted user passwords.
/etc/group	         Stores user groups.
/etc/hostname      	 Contains the system's hostname.
/etc/hosts	         Maps hostnames to IP addresses.
/etc/fstab	         Defines mount points for filesystems.
/etc/resolv.conf	   Defines DNS settings.
/etc/network/interfaces	      Configures network interfaces (in some distributions).
/etc/systemd/system/	        Stores custom systemd service files.
/etc/crontab	                Manages scheduled tasks (cron jobs).
/etc/sudoers	                Defines sudo permissions.
/etc/ssh/sshd_config	        Configures SSH server settings.


4. /tmp

storing temporary files
usually deleted automatically when the system reboots.


5. /var

stores variable data that changes frequently
example : logs, cache


/var/log/               	Stores system and application logs.
/var/tmp/	                Stores temporary files (not deleted on reboot).
/var/spool/	              Contains queues for scheduled jobs (e.g., print jobs, mail).
/var/cache/	              Stores cached data for applications.
/var/lib/	                Stores dynamic app data (e.g., databases, system states).


/dev	                       Device Files – Virtual files for hardware devices (e.g., /dev/sda, /dev/null).
/home	                       User Home Directories – Personal files and settings for users.
/lib	                       System Libraries – Shared libraries required for system binaries.
/lib64	                     64-bit System Libraries – Libraries for 64-bit architecture.
/media	                     Mount Point for Removable Media – Automounted devices like USBs and DVDs.
/mnt	                       Manual Mount Directory – Temporary mount point for external filesystems.
/opt	                       Optional Software Packages – Third-party applications installed manually.
/proc	                       Process Filesystem – Kernel and system process information (virtual filesystem).
/root	                       Root User Home – Home directory for the root (superuser).
/run	                       Runtime Variable Data – Stores runtime process information (e.g., PIDs, sockets).
/sbin	                       System Binaries – Essential system administration commands for root users.
/srv	                       Service Data – Data for system services (e.g., web server files).
/sys	                       Kernel & System Info – Exposes hardware and system details (virtual filesystem).
/usr	                       User Utilities & Applications – Contains installed programs and libraries.