Same behaviour on my xubuntu machine.
$ uname -a Linux ubuntu 2.6.20-16-generic #2 SMP Fri Aug 31 00:55:27 UTC 2007 i686 GNU/Linux $ cat /proc/version_signature Ubuntu 2.6.20-16.31-generic
Same behaviour on my xubuntu machine.
$ uname -a signature 16.31-generic
Linux ubuntu 2.6.20-16-generic #2 SMP Fri Aug 31 00:55:27 UTC 2007 i686 GNU/Linux
$ cat /proc/version_
Ubuntu 2.6.20-