How to fine Linux Running 32Bit or 64Bit Kernel or CPU

Now a days every (most of) admin wants to know which version (32bit or 64bit) of OS (Operating System) is running on his/her server either it is Linux or Windows. Also want to check the capability of CPU whither it is 32bit or 64bit.

I normally get a lot of query about other admin's server to check if they are running their required version of OS (32Bit or 64bit). Also get query to check if their hosting company give them their required 64bit CPU.

The truth is, now a days all most every CPU is capable to run 64Bit operating system.

If you want to check whether you’r server is running 32-bit or 64-bit kernel just issue some simple command


You can check it by issue 'uname' command or read '/proc/cpuinfo' file to check system information including kernel version and whether kernel is 32 bit or 64 bit.


Checking Running Kernel Version with 'uname' command: 


Open an terminal on your Linux server and issue command: 


$ uname -a


It will show output something like bellow:


Linux fortune 2.6.18-238.9.1.el5 #1 SMP Tue Apr 12 18:10:56 EDT 2011 i686 i686 i386 GNU/Linux 


i386/i486/i586/i686 indicates that you've a 32 bit Linux kernel running or output show something like: 


Linux ora100 2.6.5-7.252-smp #1 SMP Tue Feb 14 11:11:04 UTC 2006 x86_64 x86_64 x86_64 GNU/Linux


x86_64 or x86_64/GNU/Linux indicates that you've a 64bit Linux kernel running.


Note: Keep in mind that Above example is to show only the Linux Kernel version running on your server, this is not showing any hardware information. 


Checking Your Server has 32-bit or 64-bit CPU from '/proc/cpuinfo' file: 


Same as above open an terminal on your Linux server and read the content of file located on /proc/cpuinfo


/proc/cpuinfo file contain a lot of information of cpu but all are not needed to check the 32/64 bit version. You will only need 'flags:' information by Issuing following command: 


$ grep flags /proc/cpuinfo


Output will show something like: 

flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm

CPU Modes:

• lm flag means Long mode cpu - 64 bit CPU
• Real mode 16 bit CPU
• Protected Mode is 32-bit CPU

Thanks to: This nice article on 32 64 bit article!