What are Linux Directory Structure main components

    New to Linux/Unix ? Or you worked with Linux/Unix but never got deep into Linux filesystem structures and the directories ? No problem in this article i will walk you thru what is their purpose, where they are located and how we can use them !

Bellow is image of the hierarchical layout having the / at the top

I will start describing each of them starting with root aka / 

/ – 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 /.

/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.

/dev - Device Files

• The /dev directory contains the special device files for all the devices. The device files are created during installation. All hardware files are present in /dev(Device ) folder. If we observe the /dev folder you can find files/folders related to different hardware’s present in the machine.

/home – Home Directories

• Home directories for all users to store their personal files.
• For example: /home/johndoe, /home/aodba

/mnt – Mount Directory

• Temporary mount directory where sysadmins can mount filesystems.

/root - Root Home Directory

/tmp – Temporary Files

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

/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);

/boot – Boot Loader Files

• Contains boot loader related files.
• Kernel initrd, vmLinux, grub files are located under /boot

/etc – Configuration Files

• Contains configuration files required by all programs.
• This also contains startup and shutdown shell scripts used to start/stop individual programs.
• Contains device files.
• These include terminal devices, usb, or any device attached to the system.

/lib – System Libraries

• Contains library files that supports the binaries located under /bin and /sbin
• Library filenames are either ld* or lib*.so.*

/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

/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

/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

/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.

/srv – Service Data

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