How To See Ubuntu OS 32bit or 64bit. To determine whether our ubuntu is 32bit or 64bit there is 2 way to check. Accordings to askubuntu we can determine its operating system version by running :

1. uname -a
which the results in my computer is

root@dhcppc12:/sbin# uname -a
Linux dhcppc12 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:15:33 UTC 2013 i686 i686 i386 GNU/Linux

the bold words shows that it is 32 bit operating system, while it shows you x86_64 x86_64 x86_64
it means you have installed the 64 bit operating system.

2. file /sbin/init
file command is used to determine file type, it will result

root@dhcppc12:/sbin# file /sbin/init
/sbin/init: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=0x07075fcb55b05aeb6286efabba63534fa6ecd213, stripped

the bold “32-bit” shows you that this file type is 32bit
it will show you

ELF 64-bit LSB shared object, x86-64, version 1 (SYS…

instead if you have installed the 64 bit ubuntu operating system.

Determining Operating system type is different with determining hardware type.
to determine hardware type we can use command
root@dhcppc12:/sbin# lshw -c cpu | grep width
width: 64 bits
or simply type lshw -c cpu

🙂

source :
http://askubuntu.com/questions/41332/how-do-i-check-if-i-have-a-32-bit-or-a-64-bit-os