Use following check Linux OS version through command linux operating system version. There are so many linux commands which are useful but sometimes you need to know about hosting server details and their operating system.
following command will useful for fedora, centos, redhat os.
I got the following result after this command.
Linux purab-5745 3.8.0-29-generic #42-Ubuntu SMP Tue Aug 13 19:40:39 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
If you have debian OS than, you can use following command.
Normally above command will show the your kernel version information.
Following command also shows the OS version