By following the below methods we can check whether we have a 32 bit or 64 bit OS as well as hardware

A 64 bit hardware can support both 32 and 64 bit OS.But the reverse is not possible.

[username@hostname bin]$ uname -a

Linux ip-10-136-41-31 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

x86_64 GNU/Linux indicates that you've a 64bit Linux kernel running. If you use see i386/i486/i586/i686 it is a 32 bit kernel.

------------------------------------------------------------------------------------------------------------

[username@hostname bin]$ uname -m

x86_64

------------------------------------------------------------------------------------------------------------

[user@hostname bin]$ getconf   LONG_BIT

64

------------------------------------------------------------------------------------------------------------

[root@server user]# grep flags /proc/cpuinfo

flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm pni monitor ds_cpl cid xtpr

flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm pni monitor ds_cpl cid xtpr

CPU Modes:

·        lm flag means Long mode cpu - 64 bit CPU

·        Real mode 16 bit CPU

·        Protected Mode is 32-bit CPU