Ways to check Linux OS is 32 bit or 64 Bit

uname -m

x86_64 ==> 64-bit kernel
i686   ==> 32-bit kernel

/bin/uname -m

x86_64 ==> 64-bit kernel
i686   ==> 32-bit kernel

getconf LONG_BIT

64 ==> 64-bit kernel
32 ==> 32-bit kernel

arch

x86_64 ==> 64-bit kernel
i686   ==> 32-bit kernel

file /sbin/init

/sbin/init: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, stripped    ==> 64-bit kernel

/sbin/init: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), for GNU/Linux 2.6.9, stripped   ==> 32-bit kernel

In Ubuntu

dpkg --print-architecture

amd64 ==> 64-bit kernel
amd32 ==> 32-bit kernel

Ref: http://stackoverflow.com/questions/246007/how-to-determine-whether-a-given-linux-is-32-bit-or-64-bit