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I am using CentOS 6.2. In the man page of uname (i.e., man uname), it says:

 -r, --kernel-release
              print the kernel release

 -v, --kernel-version
              print the kernel version

While trying the command, it shows

[max@localhost ~]$ uname -r


[max@localhost ~]$ uname -v

#1 SMP Tue May 15 22:09:39 BST 2012

-v should show the version, right? But where is it showing the version? -r is showing the version detail.

Why is this so?

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Pls see my answer for a different point of view than slhck's. – MariusMatutiae Nov 21 at 8:49

2 Answers 2

This is absolutely normal and expected. kernel-release will always show the actual version number of the used kernel. kernel-version however will print a more specific string with the actual release date. Its format depends on which Linux or Unix distribution it's run on.

You can find an extensive list of examples on Wikipedia. For example, in OS X, the kernel-version will be not only the release number, but also the release date:

Darwin Kernel Version 10.8.0: Tue Jun  7 16:32:41 PDT 2011; root:xnu-1504.15.3~1/RELEASE_X86_64

While the kernel-release is simply the release number:


You can even check /proc/sys/kernel/ for the things uname(2) will look up when it's called by uname(1). This would be:

  • /proc/sys/kernel/version
  • /proc/sys/kernel/osrelease

Sorry for begging the question, but don't think too strictly of "version" as just a version number.

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I disagree with slhck's answer. The OP refers to the Linux kernel and, in such matters, the first reference is the Linux Kernel Organization, which

... is managed by The Linux Foundation, which provides full technical, financial and staffing support for running and maintaining the infrastructure.

The Linux Kernel site identifies the version with the progressive number, like anything preceding the dash in the output below,

$ uname -r

i.e. 3.16.0. At the same time, it identifies the release as one category among five. The first four are:


Prepatch or "RC" kernels are mainline kernel pre-releases that are mostly aimed at other kernel developers and Linux enthusiasts. They must be compiled from source and usually contain new features that must be tested before they can be put into a stable release. Prepatch kernels are maintained and released by Linus Torvalds.


Mainline tree is maintained by Linus Torvalds. It's the tree where all new features are introduced and where all the exciting new development happens. New mainline kernels are released every 2-3 months.


After each mainline kernel is released, it is considered "stable." Any bug fixes for a stable kernel are backported from the mainline tree and applied by a designated stable kernel maintainer. There are usually only a few bugfix kernel releases until next mainline kernel becomes available -- unless it is designated a "longterm maintenance kernel." Stable kernel updates are released on as-needed basis, usually 2-3 a month.


There are usually several "longterm maintenance" kernel releases provided for the purposes of backporting bugfixes for older kernel trees. Only important bugfixes are applied to such kernels and they don't usually see very frequent releases, especially for older trees.

These are the official release designations. However, you are unlikely to have any of those, because there is also a fifth kind of release. Again as per the previously referenced page,

Distribution kernels

Many Linux distributions provide their own "longterm maintenance" kernels that may or may not be based on those maintained by kernel developers. These kernel releases are not hosted at and kernel developers can provide no support for them.

It is easy to tell if you are running a distribution kernel. Unless you downloaded, compiled and installed your own version of kernel from, you are running a distribution kernel. To find out the version of your kernel, run uname -r:

# uname -r

If you see anything at all after the dash, you are running a distribution kernel. Please use the support channels offered by your distribution vendor to obtain kernel support.

If you want to know which official release your distro-customised kernel is based upon, there is one such list on the Linux Kernel main page.

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