You can find your Kernel version with uname -a but it wont say if your operating system is Centos, Redhat, Ubuntu 9 or Debian 5. To display os-details we can read the content from /proc/version.
cat /proc/version
Linux version 2.6.26-2-amd64 (Debian 2.6.26-19lenny1) (dannf@debian.org) (gcc version 4.1.3 20080704 (prerelease) (Debian 4.1.2-25)) #1 SMP Mon Oct 19 02:34:17 UTC 2009