uname command

[joemon]

Hi,

uname -a command prints the following:
Linux hostname kernel_ver #1 SMP Thu May 8 10:52:19 EDT 2008 i686 i686 i386 GNU/Linux

I could see "i686 i686 i386" in the output. I do understand that i386 indicates that I am using a 32 bit kernel. & i686 shows that I am using 64 bit processor. But why I do I see i686 twice. I just presumed that it could be bcoz I am using 2 processors. But infact there are 4 processors in my server.
Please comment on this.

[robertdaleweir]

Hi,

uname -a command prints the following:
Linux hostname kernel_ver #1 SMP Thu May 8 10:52:19 EDT 2008 i686 i686 i386 GNU/Linux

I could see "i686 i686 i386" in the output. I do understand that i386 indicates that I am using a 32 bit kernel. & i686 shows that I am using 64 bit processor. But why I do I see i686 twice. I just presumed that it could be bcoz I am using 2 processors. But infact there are 4 processors in my server.
Please comment on this.

Hi joemon
The man pages gives the information on what is printed with the -a option.
--->
UNAME(1) User Commands UNAME(1)

NAME
uname - print system information

SYNOPSIS
uname [OPTION]...

DESCRIPTION
Print certain system information. With no OPTION, same as -s.

-a, --all
print all information, in the following order, except omit -p and -i if unknown:

-s, --kernel-name
print the kernel name

-n, --nodename
print the network node hostname

-r, --kernel-release
print the kernel release

-v, --kernel-version
print the kernel version

-m, --machine
print the machine hardware name

-p, --processor
print the processor type or "unknown"

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

-o, --operating-system
print the operating system

--help display this help and exit

--version
output version information and exit
<---
Essentially the three you are asking about are a) processor (option -p) b) hardware platform (option -i) and c) operating system (option -o). Hope this helps. Cheers...
Robert

[joemon]

Thanks for the reply. The information that you have given is incorrect...Also the man page for this command doesn't seems to a simple answer to my doubts. May I know what is the difference between "hardware platform" (which is i386) & "machine hardware name" (which is i686) in the above example.

[HROAdmin26]

No, i686 does *not* indicate a 64 bit processor.

I will not go through every possible version of the uname command, but you can refer to the uname manual on your own system.

An example:

uname --version
uname (coreutils) 5.2.1

uname --help
Usage: uname [OPTION]...
Print certain system information.  With no OPTION, same as -s.

  -a, --all                print all information, in the following order:
  -s, --kernel-name        print the kernel name
  -n, --nodename           print the network node hostname
  -r, --kernel-release     print the kernel release
  -v, --kernel-version     print the kernel version
  -m, --machine            print the machine hardware name
  -p, --processor          print the processor type
  -i, --hardware-platform  print the hardware platform
  -o, --operating-system   print the operating system
      --help     display this help and exit
      --version  output version information and exit

uname -a
Linux SYSTEM 2.6.5-7.308-default #1 Mon Dec 10 11:36:40 UTC 2007 i686 athlon i386 GNU/Linux

[vishesh]

"i386", "i486", "i586" and "i686" and "athlon" all mean 32 bit.
i686 generally refer xeon processor .

execute following
#more /proc/cpuinfo|grep flags, if 'lm' word present in output that means you have 64 bit cpu otherwise you have 32 bit cpu.

thnks

[HROAdmin26]

"i386", "i486", "i586" and "i686" and "athlon" all mean 32 bit.
i686 generally refer xeon processor .

execute following
#more /proc/cpuinfo|grep flags, if 'lm' word present in output that means you have 64 bit cpu otherwise you have 32 bit cpu.

thnks

Yes, if those are listed in the "uname" output of a Linux system, it does indicate the Linux install is 32 bit. A 64 bit Linux install will have x86_64 in the uname results.

As for the actual processor, i686 refers to the 6TH generation of Pentium processor architecture that goes back to the Pentium Pro - and some of them are 64 bit.

[vishesh]

i think 'uname -m' set set by setarch rpm. as we can see using man command
root#man setarch

So what we get in uname is basically collected by rpm and it may show wrong result or 32 bit os is running on 64 bit cpu architecture ?


thnks

[joemon]

Hi vishesh,

I've heard that if lm is listed as one of the flags in cpuinfo, it is a 64 bit processor & if tm is listed it is a 32 bit processor. But what if both these flags are lised ?

************************************************** *******
cat /proc/cpuinfo |grep flags
flags : fpu vme de pse tsc msr pae mce cx8 apic 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 vmx smx est tm2 cx16 xtpr lahf_lm
************************************************** *******

[vishesh]

Its now sure that you have 64 bit cpu.
I am not sure about tm but 'lm' denote long mode that is 64 bit cpu.
post complete output of /proc/cpuinfo
you can also use 'dmidecode' command for more detail result
#man dmidecode

thnks

(There may be case that your cpu support 64 bit but motherboard have 32 bit architecture, surely not concluded from 'tm' )

[HROAdmin26]

i think 'uname -m' set set by setarch rpm. as we can see using man command
root#man setarch

So what we get in uname is basically collected by rpm and it may show wrong result or 32 bit os is running on 64 bit cpu architecture ?


thnks

Uname is a reflection of the currently running Linux OS and how it was compiled.