Linux File System Hierarchy Standards (FHS)

  1. / – Root 
    • Every single file and directory starts from the root directory
    • Only root user has write privilege under this directory.
  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 administrator, 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/sysconfig/network-scripts/ifcfg-eth0
  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 file system contains information about running process. For example: /proc/{pid} directory contains information about the process with that particular pid.
    • This is a virtual file system 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 level programs.
    • /usr/bin contains binary files for user programs. If you can’t
    • binary under /bin, look under /usr/bin. For example: at, awk, cc, less, scp
    • /usr/sbin contains binary files for system administrators. If you 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 /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 file systems.
  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.

References :- From Laxman sir’s Note 😀 .

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