172

uname -m gives i686 and uname -m gives i686 i386 output in Red Hat Enterprise Linux Server release 5.4 (Tikanga) machine. I need to install Oracle Database 10g Release 2 on that machine. So, how can I decide whether kernel architecture is 32bit or 64bit?

6

12 Answers 12

154

i386 and i686 are both 32-bit.
x86_64 is 64-bit

example for 64 bit:

behrooz@behrooz:~$ uname -a  
Linux behrooz 2.6.32-5-amd64 #1 SMP Mon Mar 7 21:35:22 UTC 2011 **x86_64** GNU/Linux

EDIT:
See is my linux ARM 32 or 64 bit? for ARM

5
  • What about armv7l? In any case, a command with a simple boolean response would be delicious.
    – user7543
    Oct 26, 2013 at 23:40
  • 1
    @user7543 It's ARM 32-bit, because we don't have 64-bit ARM yet.When we do, It's gonna be something different.
    – Behrooz
    Oct 27, 2013 at 7:38
  • I feel like I should make my answer community wiki but don't know how.
    – Behrooz
    Dec 26, 2014 at 21:20
  • 15
    Try: uname -m. That'll only show the architecture. Nov 18, 2016 at 14:29
  • arm64 is called aarch64
    – xdevs23
    Nov 16, 2019 at 13:26
90

It's simple! Use the arch command from coreutils package.

5
41

For Debian:

On my PC

    ~ > dpkg --print-architecture
    amd64
    ~ > dpkg --print-foreign-architectures
    i386

My Raspberry Pi 2

    ~ > dpkg --print-architecture
    armhf
4
  • 2
    this works best when determining package architecture to use with checkinstall, thx! Feb 11, 2016 at 1:59
  • 2
    Thank you. I've been looking for something that would drop the 'standard' "amd64"/"i386" architecture names rather than just "x86_64". No one uses that terminology when naming precompiled releases.
    – Cliff
    Jul 11, 2019 at 19:25
  • Does CentOS/RedHat have an equivalent command? Or is this a problem on RH-based OSes? Trying to add support to an ansible role for the RH family to expand OS options for future servers.
    – Zack
    Dec 20, 2020 at 20:48
  • Much better for me, thanks! May 27 at 10:46
34

@behrooz is correct. Unfortunately uname requires you to know architectures. Actually, I was looking for a list of architectures and I found this article that answers your question. In regards to uname -m:

x86_64 GNU/Linux indicates that you've a 64bit Linux kernel running. If you use see i386/i486/i586/i686 it is a 32 bit kernel.

To determine if the hardware is capable of running a 64-bit kernel

grep flags /proc/cpuinfo

Look for the following in the output (all flags retrieved from this stackoverflow answer for the same question )

  • lm flag means Long mode cpu - 64 bit CPU
  • tm flag means Protected mode - 32-bit CPU
  • rm flag means Real Mode - 16 bit CPU
7
  • Does the lm flag simply mean the CPU supports 64-bit or does it mean that it's running in 64-bit. I recommend relying on the arch knowing that it will be x86_64 for 64-bit or i?86 for 32-bit.
    – penguin359
    May 2, 2011 at 21:45
  • 1
    @penguin359 it means that the cpu supports 64-bit. May 2, 2011 at 22:57
  • @xeno so then is can't be used to determine the kernel architecture.
    – penguin359
    May 2, 2011 at 23:58
  • @penguin359 no, was that unclear in the answer? May 3, 2011 at 8:55
  • 2
    @penguin359, no but it's often useful to find out if your OS is running 64-bit and if not if the hardware is capable, imo May 3, 2011 at 20:09
14

The simplest way is to run:

getconf LONG_BIT

which will output 64 or 32 depending on whether it is 32 or 64 bits.

eg:

dannyw@dannyw-redhat:~$ getconf LONG_BIT
64
1
  • 4
    This answer is misleading. If you enable multiarch support and install 64 bit kernel over 32 bit installation getconf LONG_BIT will print 32 though you are running 64 bit kernel.
    – kenn
    Jul 23, 2018 at 7:42
2

use syscap from Formake project

syscap allows to probe many system properties and test dependencies. It is a portable shell script.

Get CPU architecture:

syscap info -arch

Get kernel name and version:

syscap info -kernel -kernver
1

Another way is to check the architecture some system file was compiled for, like

$ file /usr/bin/ld
/usr/bin/ld: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, stripped
4
  • 1
    That's the system architecture, which isn't always the kernel architecture. See this answer at SU for more variations. May 4, 2011 at 9:47
  • Theoretically, they may differ, but is there a chance they would mismatch on any real-life installation?
    – minaev
    May 5, 2011 at 11:30
  • Some distributions ship an amd64 kernel on the x86 version. I don't know how many people use them, I checked Debian popcon but it doesn't correlate between the various stats. I think the main use case is having a 32-bit main OS and running a 64-bit OS in a chroot or in a VM. May 5, 2011 at 20:00
  • @Gilles You're gonna love what you'll read about the new x32 architecture, If I'm not too late, off course. wiki.debian.org/X32Port
    – Behrooz
    Oct 27, 2013 at 7:41
1

Or you can use the way of what the uname command internally does if you want to implement some stuff on your own:

#include <sys/utsname.h>
#include <stdio.h>

int main() {
    struct utsname name;
    uname(&name);
    printf("%s\n",name.machine);
    return 0;
}
1

If you're looking for a simple one-liner, this is the most reliable solution that I've found that returns 64 or 32. It doesn't care if you're running ARM or not, and it should work on any system using bash or sh.

Beware, this will assume the system is either 32-bit or 64-bit. See my explanation below if you need to detect 8- 16- or some-other-bit architecture.

[ $((0xffffffff)) -eq -1 ] && echo 32 || echo 64

What's happing here?
The logic is very simple and it all boils down to how computers store signed integers. A 32-bit architecture only has 32 bits that it can use for storing signed integers while a 64-bit architecture has 64 bits! In other words the set of integers that can be stored is finite. Half of this set represents negative numbers and half represents positive numbers. The signed integer equalling -1 is represented as the largest number that can be stored in a given number of bits for that architecture. On a 32-bit system, -1 can be represented by the hex value 0xFFFFFFFF (which is 32 binary bits, all equalling 1). On a 64-bit system, 0xFFFFFFFF translates to 4,294,967,295, base 10 while 0xFFFFFFFFFFFFFFFF is the representation for -1). You can see how this would easily scale for systems that are 8- or 16-bit as well which would equal -1 at 0xFF and 0xFFFF, respectively.

1

For debian Linux derived systems.

On 64bits systems :

$ dpkg-architecture -q DEB_BUILD_ARCH
amd64

On 32bits systems :

$ dpkg-architecture -q DEB_BUILD_ARCH
i386
1

There is also lscpu: display information about the CPU architecture

lscpu
Architektura:                    x86_64
Tryb(y) pracy CPU:               32-bit, 64-bit
Kolejność bajtów:                Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU:                             8
Lista aktywnych CPU:             0-7
Wątków na rdzeń:                 2
Rdzeni na gniazdo:               4
Gniazd:                          1
Węzłów NUMA:                     1
ID producenta:                   GenuineIntel
Rodzina CPU:                     6
Model:                           60
Nazwa modelu:                    Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz
Wersja:                          3
CPU MHz:                         3392.293
CPU max MHz:                     3900,0000
CPU min MHz:                     800,0000
BogoMIPS:                        6784.24
Wirtualizacja:                   VT-x
Cache L1d:                       128 KiB
Cache L1i:                       128 KiB
Cache L2:                        1 MiB
Cache L3:                        8 MiB
Procesory węzła NUMA 0:          0-7
0

Here's another method using uname.

From uname(1):

...

    -i, --hardware-platform
      print the hardware platform or "unknown"
...

# uname -i
x86_64

#
1
  • 1
    Until it gives "unknown"
    – Dagelf
    Jul 5, 2019 at 19:22

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