How Do I Know if I’m Running 32-bit or 64-bit Linux?

If you’ve bought a new computer recently, you probably have a 64-bit processor and installed the 64-bit version of your Linux distribution. What if your computer is a bit older and you don’t remember?
There is a nice and simple command line program called uname that will tell us exactly that.
Open a terminal window (Applications > Accessories > Terminal).

In the terminal window, type in

uname –m

and hit enter.

• If the response is i686, you have a 32-bit version of Linux.
• If the response is x86_64, you have a 64-bit version of Linux. 

Note: if you get some other value like i386, you almost certainly have a 32-bit version of Linux.
You can find out more detail about your particular installation of Linux, like your kernel version, by entering

uname –a

 Thanks to niteshifter and overdrank from this Ubuntu forums thread for this information.