So, how can you tell if the system you are using is 64-bit capable under Linux or just x86?

It’s easy. Run the following command:

$ cat /proc/cpuinfo | grep -y flags

In the output, look for the ‘lm’ (that’s L M) flag.

$ cat /proc/cpuinfo | grep -y flags
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 cid 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 cid cx16 xtpr lahf_lm

The ‘lm’ flag stands for “Long Mode” and is only present on 64-bit processors, and determines that you have the capability of running a 64-bit OS. This is from thefollowing:

/usr/include/asm/cpufeature.h: #define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */

Particularly, on my local system, which runs 32-bit Ubuntu Feisty, I found that the file containing this was in /usr/src/linux-headers-VERSION/includes.

It seems I may have a box to rekick soon, just to give it a whirl.

/cs