Linux file system structure
/ – The Root Directory
Everything on Linux system is located
under the / or root directory. The meaning of / or root and root user
are often confusing to new Linux users. In Linux, the root directory “/”
(The tree of the file system starts at the trunk or slash, indicated by
a forward slash /) is a separator between a file and a directory
contains all underlying directories and files, yet root user is a super
user or administrator user with has administrative privileges on the
system vs Linux privileged users who only have limited privileges to
protect system security.
/bin – Essential command binaries
The
/bin directory is a place contains most commonly essential executable
terminal binaries programs or file required during booting, repairing
like cat, ls, mount, rm, du, df, tar, rpm, wc, etc.
/boot – Boot loader files
All
of the required files to boot the system contains in /boot directory,
including GRUB boot loader’s files, Linux kernels, the Linux initial RAM
disk (initrd),
/dev – Device Files
All of the hardware
devices on the machine like cdrom, cpu, hard drives, etc will be stored
as special device files that represent all the devices in /dev
directory. Device files are created during your Linux system
installation.
/etc – Configuration Files
Contain
host-specific files and directories, e.g. information about system and
application configuration files like startup, shutdown, start, stop
script for every individual program. In another word /etc data is very
similar to Control panel in Microsoft Windows.
/home – Home Directory
Home
directory of the users. Every time you create a new user, a new
directory with user’s name is created in /home directory for users to
store their own files within their own home’s directory. Most common
automatic directories created within /home ‘s user are Desktop,
Downloads, Documents, Music, Movie, etc. Most programs configuration
file for a specific user will be saved in it’s users /home directory
like web browser settings, web browser bookmarks, desktop wallpaper,
themes, and passwords.
/lib – Essential Libraries
Similar
to Windows ‘dll’ files, all Linux shared libraries and kernel modules
files stores in /lib directory. These important Linux dynamic libraries
are required to boot the system and run commands in the root file
system.
/lost+found – Recovering Files
Sounds weird but
yes we have lost+found in Linux file system structure. Every Linux file
system and partitions has a lost+found in it’s directory. In the even
your system is crashed or unexpected shutdown, you can run fsck command
to check and repair the filesystem, fsck will turn any corrupted or
almost-deleted files back into files that you can recover them later in
/lost+found directory.
/media – Removable Media Devices
Every
time you insert a removable device such as external hard drive, floppy
disk, zip drive, CDs, DVDs, flash drive to a Linux system, a new
directory will automatically be created inside the /media directory.
/media directory is a temporary mount directory for removable devices.
/mnt – Temporarily mounted filesystems
While
/media is where the system automatically mounts removable media, /mnt
is for you to mount things (partitions, file systems, devices) manually
and temporarily.
/opt – Optional software packages
The
/opt directory is reserved to store addition software or extra and
third-party software for your system, those addition software usually
don’t follow the standard file system hierarchy and not handled by the
package manager.
/proc – Kernel & Process Information
Similar
to /dev, /proc directory contains information about running process,
system resources and information. You can view information about any
running process with a specific process-id (pid) or hardware’s
information such as memory, cpu, io, etc…
/root – Root Home Directory
Don’t
be confused with “/” or root directory, /root is a root account’s home
directory determined by developer or local preference rather than
/home/root to allow for booting the system even if /home/ is not
available.
/sbin – System binaries
Similar to /bin, /sbin
contains essential binaries that are generally intended to be run by the
root user for system administration and maintenance purpose. For
example: iptables, reboot, fdisk, ifconfig, swapon, init, ip, mount
/selinux – Security-Enhanced Linux
Selinux
comes with RedHat based distro (fedora, centos), selinux is a security
architecture integrated into the 2.6.x kernel using the Linux Security
Modules (LSM). For some reason Centos 6 created an emtpry selinux
directory in root directory, the real selinux directory with its
configuration files are stored in /etc/selinux/ directory.
/srv – Service Data
Server (srv) contains data of services such as HTTP, FTP, rsync, cvs
/sys – virtual filesystem
Some
newer Linux distros have /sys directory with sysfs virtual filesystem
to store information and statistics about (physical and virtual) device
and device names. /sys is newly added since Linux kernel 2.6 /sys
contains similar information with /proc which display device information
about the kernel’s view of the system.
/tmp – Temporary files
System’s
Temporary Directory, all users and programs in your system can
access/read/write in this directory. You should not save/store any
important files/directories under /tmp since all files will be removed
after system is rebooted.
/usr – binaries, documentation, source code, libraries
Pronounced
as ‘user’, /usr contains the majority of user utilities, programs,
libraries, documentation etc for all user-related second level programs
rather than applications and files used by the system.
/var – Variable Files
Variable or /var contains data that is expected to change and grow as the system is running (log, mail, spool, temp)
Ref:http://www.namhuy.net/3230/linux-file-system-structure.html
