Understanding inode in Linux

I just wanted to keep myself acquainted with this inode.



What is inode?
In computing, an inode (index node) is a data structure found in many Unix file systems. Each inode stores all the information about a file system object (file, device node, socket, pipe, etc.), except data content and file name. (from Wikipedia). 

From Cyberciti.biz,
An inode is a data structure on a traditional Unix-style file system such as UFS or ext3. An inode stores basic information about a regular file, directory, or other file system object.


So as what I understand, how does Linux stores the file and allocates a an index for its file system data structure  is thru index nodes (or inodes) (It's not clear if  i stands for index anyway, but it's easy if we term it i as "index"). 

inodes does not, "contain file names, only file metadata".

Unix directories are lists of association structures, each of which contains one filename and one inode number.

When searching for a filename, this means that, 

• The file system driver must search a directory looking for a particular filename and then convert the filename to the correct corresponding inode number.

Additionally, The operating system kernel's in-memory representation of this data is called struct inode in Linux. Systems derived from BSD use the term vnode, with the v of vnode referring to the kernel's virtual file systemlayer.

For more info, read on WIkipedia (https://en.wikipedia.org/wiki/Inode).

From Cyberciti.biz, this is what an inode contains,

• File type (executable, block special etc)
• Permissions (read, write etc)
• Owner
• Group
• File Size
• File access, change and modification time (remember UNIX or Linux never stores file creation time, this is favorite question asked in UNIX/Linux sys admin job interview)
• File deletion time
• Number of links (soft/hard)
• Extended attribute such as append only or no one can delete file including root user (immutability)
• Access Control List (ACLs)

Remember that, each inode is identified by a unique inode number within the file system. Inode is also know as index number.

Commands that are helpful to bring the inode along with the filename are:

# ls -i filename

783365 -rw-r--r--. 1 geekgogie   geekgogie         165 Jul 18 07:20 stats

# find -inum 783365

./stats

Helpful urls:
http://www.linux-mag.com/id/8658/
http://en.wikipedia.org/wiki/Inode_pointer_structure
http://www.thegeekstuff.com/2012/01/linux-inodes/
http://www.linfo.org/inode.html