What's the difference between "uname -r" and "uname -v"?

Question

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

2.6.32-220.17.1.el6.i686

[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?

Solution

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:

10.8.0

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

Don't think too strictly of "version" as just a version number.

Comments

[don_crissti]

Obviously the right answer, whether the other poster disagrees or not.