Filesystem Hierarchy Standard (Directory Structure)

The Filesystem Hierarchy Standard (FHS) defines the directory structure and directory contents in Unix and Unix-like operating systems, maintained by the Linux Foundation.

/ – Root

    Every single file and directory starts from the root directory.
    Only root user has write privilege under this directory.
    Please note that /root is root user’s home directory, which is not same as /.

2. /bin – User Binaries

    Contains binary executables.
    Common linux commands you need to use in single-user modes are located under this directory.
    Commands used by all the users of the system are located here.
    For example: ps, ls, ping, grep, cp.

3. /sbin – System Binaries

    Just like /bin, /sbin also contains binary executables.
    But, the linux commands located under this directory are used typically by system aministrator,

    for  system maintenance purpose.
    For example: iptables, reboot, fdisk, ifconfig, swapon

4. /etc – Configuration Files

    Contains configuration files required by all programs.
    This also contains startup and shutdown shell scripts used to start/stop individual programs.
    For example: /etc/resolv.conf, /etc/logrotate.conf

5. /dev – Device Files

    Contains device files.
    These include terminal devices, usb, or any device attached to the system.
     For example: /dev/tty1, /dev/usbmon0

6. /proc – Process Information

    Contains information about system process.
    This is a pseudo filesystem contains information about running process. For example:

    /proc/{pid}

    directory contains information about the process with that particular pid.
    This is a virtual filesystem with text information about system resources. For example:

    /proc/uptime

7. /var – Variable Files

    var stands for variable files.
    Content of the files that are expected to grow can be found under this directory.
    This includes — system log files (/var/log); packages and database files (/var/lib); emails

    (/var/mail); print queues (/var/spool); lock files (/var/lock); temp files needed across reboots

    (/var/tmp);

8. /tmp – Temporary Files

    Directory that contains temporary files created by system and users.
    Files under this directory are deleted when system is rebooted.

9. /usr – User Programs

    Contains binaries, libraries, documentation, and source-code for second level programs.
    /usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look

     under /usr/bin. For example: at, awk, cc, less, scp
    /usr/sbin contains binary files for system administrators. If you can’t find a system binary under

    /sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel
    /usr/lib contains libraries for /usr/bin and /usr/sbin
    /usr/local contains users programs that you install from source. For example, when you install

     apache from source, it goes under /usr/local/apache2

10. /home – Home Directories

     Home directories for all users to store their personal files.
     For example: /home/john, /home/nikita

11. /boot – Boot Loader Files

    Contains boot loader related files.
    Kernel initrd, vmlinux, grub files are located under /boot
    For example: initrd.img-2.6.32-24-generic, vmlinuz-2.6.32-24-generic

12. /lib – System Libraries

    Contains library files that supports the binaries located under /bin and /sbin
    Library filenames are either ld* or lib*.so.*
    For example: ld-2.11.1.so, libncurses.so.5.7

13. /opt – Optional add-on Applications

    opt stands for optional.
    Contains add-on applications from individual vendors.
    add-on applications should be installed under either /opt/ or /opt/ sub-directory.

14. /mnt – Mount Directory

    Temporary mount directory where sysadmins can mount filesystems.

15. /media – Removable Media Devices

    Temporary mount directory for removable devices.
    For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD 
    writer

16. /srv – Service Data

    srv stands for service.
    Contains server specific services related data.
    For example, /srv/cvs contains CVS related data.