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How can I find out that my CPU supports 64bit operating systems under Linux, e.g.: Ubuntu, Fedora?

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possible duplicate of How come I installed Ubuntu 64 bit on a Pentium 4 machine? – Gilles Jun 4 '11 at 9:57
More generally, see What do the flags in /proc/cpuinfo mean? – Gilles Jul 20 '12 at 1:45
Once you have checked the flags, then install the kernel package. Debian and Ubuntu, can run a 64bit kernel with a 32 bit userland. Installing the kernel is quick. Do not remove the old 32bit one, as you may need to go back to it. – richard Jul 11 at 8:03
up vote 24 down vote accepted


grep flags /proc/cpuinfo

Find 'lm' flag. If it's present, it means your CPU is 64bit and it supports 64bit OS. 'lm' stands for long mode.

Alternatively, execute:

grep flags /proc/cpuinfo | grep " lm "

Note the spaces in " lm ". If it gives any output at all, your CPU is 64bit.

Update: You can use the following in terminal too:

lshw -C processor | grep width

This works on Ubuntu, not sure if you need to install additional packages for Fedora.

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Afaik it won't work if "lm" is the last flag in the line. :-) – peterh Jun 27 at 12:38

I think the easiest way is by:

lscpu|grep "CPU op-mode"
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This answer is the best. It shows you an explicit "32-bit" or "64-bit". I don't see why people choose the other answer over this one. You don't even need to grep anything. Just doing lscpu is so simple. If they don't have the lscpu command then I could see why they voted for the other one. – trusktr Jan 4 '14 at 21:12
The command that is the most portable across the largest variety of platforms is arguably the most useful. – Benjamin Goodacre Sep 9 '14 at 9:06
I got '32-bit, 64-bit' What does it mean? – dstonek Apr 10 at 13:31

If your CPU is a 64bit one (x86-64), you can use it with a 64 bit OS.

Here is a list of 64bit CPUs: http://en.wikipedia.org/wiki/64-bit#Current_64-bit_microprocessor_architectures

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This is the ultra slow way, and not guaranteed to give you an answer. – trusktr Jan 4 '14 at 21:12
@trusktr: Yes. but all the other ways require Linux to be installed already. Not much help if you have an old Win32 machine and want to know if it will run a 64 bit *nix OS – Clifford May 9 '14 at 19:56
Same here. Found this useful, not having a running OS on the system in question to test it with. – ELLIOTTCABLE Oct 28 '14 at 0:38

Don't rely on the high scoring answers to this question because these methods are not always correct.

I've a computer with a Intel Atom N230 CPU which according to all of the tests mentioned is capable to support 64 bit OS'es.

According to http://en.wikipedia.org/wiki/Intel_Atom#32-bit_and_64-bit_hardware_support the CPU is not capable of running 64 bit OS'es. I've tried to install a 64 bit Linux OS and it indeed refuses to do so. Installing a 32 bit Linux OS works.

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