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What command do I type in to check this?

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up vote 9 down vote accepted

Is this a Linux server? If so, try uname -p


$ uname -p

Note that this only tells you about the Linux kernel, not any particular user-land software (e.g. you can still run 32-bit MySQL on 64-bit Linux). And you could be running 32-bit Linux on a 64-bit CPU.

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D'oh. I just saw the "linux" tag, so of course it's a Linux server :-). – Matt Solnit Oct 8 '09 at 21:37

You could also check the cpuinfo and look for the "lm" (long mode) flag

less /proc/cpuinfo


flags : ... lm ....

a 32-bit processor won't have this flag.

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Could be a 32-bit distribution on a 64-bit processor – Julien Oct 8 '09 at 23:34
Look at this thread:… – jomey Oct 9 '09 at 0:19

In addition to Matt's answer about your kernel, if you're running a Red Hat/CentOS RPM-based distro (which is what most of Rackspace is, typically) you can check the installed userland tools for their bitness with this command:

rpm -qa --queryformat='%{n}-%{v}-%{r}.%{arch}\n' | sort

You're looking for .i386 or .x86_64 on the end. It's entirely possible to have a mix of 32bit and 64bit on a 64bit install based on needs of the server.

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