Occasionally you may need to check to see if you’re running 32-bit or 64-bit Linux installation, such as when you’re installing third-party software and they offer 64-bit specific versions.
Fortunately, there’s a very easy way to tell. Simply open a terminal and run the following command:
You’ll receive one of the following as output:
i386 indicates 32-bit.
x86_64 indicates 64-bit.
Note that this only states what OS version you’re running, and not necessary the capabilities of the hardware — such can be the case if you installed 32-bit Linux on 64-bit hardware.
If you want to find out if your processor actually supports the 64-bit instruction set (‘long mode’), run the following:
cat /proc/cpuinfo | grep 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 syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm arat dts tpr_shadow vnmi flexpriority ept vpid
The ‘lm’ in the flags indicates 64-bit support. Without it, the processor is certainly 32-bit.