The base of the Linux/Unix file system hierarchy begins at the root and everything starts with the root directory.
These are the common top-level directories associated with the root directory: /bin – binary or executable programs. /etc – system configuration files. /home – home directory. It is the default current directory. /opt – optional or third-party software. /tmp – temporary space, typically cleared on reboot. /usr – User related programs. /var – log files. Some other directories in the Linux system: /boot- It contains all the boot-related information files and folders such as conf, grub, etc. /dev – It is the location of the device files such as dev/sda1, dev/sda2, etc. /lib – It contains kernel modules and a shared library. /lost+found – It is used to find recovered bits of corrupted files. /media – It contains subdirectories where removal media devices inserted. /mnt – It contains temporary mount directories for mounting the file system. /proc – It is a virtual and pseudo-file system to contains info about the running processes with a specific process ID or PID. /run – It stores volatile runtime data. /sbin – binary executable programs for an administrator. /srv – It contains server-specific and server-related files. /sys – It is a virtual filesystem for modern Linux distributions to store and allows modification of the devices connected to the system. Exploring directories and their usability: We know that Linux is a very complex system that requires an efficient way to start, stop, maintain and reboot a system, unlike Windows operating system. In the Linux system some well-defined configuration files, binaries, man pages information files available for every process.
Linux Kernel File: /boot/vmlinux – The Linux kernel file. Device Files: /dev/hda – Device file for the first IDE HDD. /dev/hdc – A pseudo-device that output garbage output is redirected to /dev/null. System Configuration Files: /etc/bashrc – It is used by bash shell that contains system defaults and aliases. /etc/crontab – A shell script to run specified commands on a predefined time interval. /etc/exports – It contains information on the file system available on the network. /etc/fstab – Information of the Disk Drive and their mount point. /etc/group – It is a text file to define Information of Security Group. /etc/grub.conf – It is the grub bootloader configuration file. /etc/init.d – Service startup Script. /etc/lilo.conf – It contains lilo bootloader configuration file. /etc/hosts – Information of IP and corresponding hostnames. /etc/hosts.allow – It contains a list of hosts allowed accessing services on the local machine. /etc/host.deny – List of hosts denied to access services on the local machine. /etc/inittab – INIT process and their interaction at the various run level. /etc/issue – Allows editing the pre-login message. /etc/modules.conf – It contains the configuration files for the system modules. /etc/motd – It contains the message of the day. /etc/mtab – Currently mounted blocks information. /etc/passwd – It contains username, password of the system, users in a shadow file. /etc/printcap – It contains printer Information. /etc/profile – Bash shell defaults. /etc/profile.d – It contains other scripts like application scripts, executed after login. /etc/rc.d – It avoids script duplication. /etc/rc.d/init.d – Run Level Initialisation Script. /etc/resolv.conf – DNS being used by System. /etc/security – It contains the name of terminals where root login is possible. /etc/skel – Script that initiates new user home directory. /etc/termcap – An ASCII file that defines the behavior of different types of the terminal. /etc/X11 – Directory tree contains all the conf files for the X-window System. User Related Files: /usr/bin – It contains most of the executable files. /usr/bin/X11 – Symbolic link of /usr/bin. /usr/include – It contains standard include files used by C program. /usr/share – It contains architecture independent shareable text files. /usr/lib – It contains object files and libraries. /usr/sbin – It contains commands for Super User, for System Administration. Virtual and Pseudo Process Related Files: /proc/cpuinfo – CPU Information /proc/filesystems – It keeps the useful info about the processes that are running currently. /proc/interrupts – it keeps the information about the number of interrupts per IRQ. /proc/ioports – Contains all the Input and Output addresses used by devices on the server. /proc/meminfo – It reports the memory usage information. /proc/modules – Currently using kernel module. /proc/mount – Mounted File-system Information. /proc/stat – It displays the detailed statistics of the current system. /proc/swaps – It contains swap file information. Version Information File: /version – It displays the Linux version information. Log Files: /var/log/lastlog – It stores user last login info. /var/log/messages – It has all the global system messages. /var/log/wtmp – It keeps a history of login and logout information.
