There are couple of ways to determine the Ubuntu version your machine is running.
- cat /etc/lsb-release
- cat /etc/issue
Out of this the lsb-release seems to be the most comprehensive.
$ cat /etc/lsb-release
and the /etc/issue the most terse.
$ cat /etc/issue
Ubuntu 8.10 n l
The uname command provides the version of Linux distribution.
$ uname -r
The uname -m option will help you determine if you are running the 32-bit version or 64-bit version of Ubuntu.
$ uname -m
Apparently if you are running a 64-bit version (on a 64-bit machine), you should get something like x86_64 as the result.