To check the version date of your OS (Linux distros):
uname -v
To find out the release:
uname -r
To display and show the complete kernel signature of your hosting server:
uname -a
Something like this will output similar information concerning your Linux kernel:
cat /proc/version
If you haven’t had the uname utility installed, you can get the kernel release version by:
cat /proc/sys/kernel/osrelease
You may also be interested in some other useful things to see within /proc.