Linux Kernel Version Numbering Methodology

Linux Kernel Version numbering Mechanism:

We can differentiate linux kernel using its version and these versions are mainly two types.

1. Stable version
2. Development version

At any point of time, we have many stable linux versions but only one development version.

Linux kernel version numbering system follows a 4 number system
X.Y.Z.W

X --> Kernel Version.
It is incremented when
a really significant changes happen in Kernel
major changes in the concepts and the code of the kernel.

Y --> Major revision of the kernel.
If this number is an even number then it is a stable kernel (Production use)
If it is odd then it is a development kernel
Developers actively work on Development kernel only.
Example: Current stable version is 2.4.x, and development version is 2.5.x
Once the development in 2.5.x is done, eventually it will become 2.6.0 kernel and new stable kernel is then established.
So, 2.7.x series will begun for development.
If only major changes happen, 2,5,x become 3.0.0 and 3.1.x is open for developers.

Z --> Minor revision of the kernel
It will be changes when a new feature or driver is added.

W --> Represents corrections such as security patches and bug fixes.

We can use "uname" command with option "r" to see which release of the kernel is being used in our linux system.
uname -r
Result in my pc: 2.6.32-28-generic

Reference:
http://www.tldp.org/FAQ/Linux-FAQ/kernel.html#linux-versioning
http://www.linfo.org/kernel_version_numbering.html