How to understand kernel 32 or 64 bit?

[Tim Frost]

On Mon, 2009-08-17 at 10:01 +0300, a bv wrote:
> Hi list,
> 
> How can i understand on an installed system if the kernel is 32 or 64
> bit , and running.

If you have a 64-bit CPU, it is possible to have either a 32-bit or a
64-bit version kernel (and therefore system).  If the command 'uname -m'
reports "x86_64", then you are running a 64-bit kernel.

On a system with a 64-bit CPU, if you are running a 32-bit kernel, the
output of 'uname -m' will be the same as for a recent 32-bit CPU (both
will report "i686" in this case).  You need to check the model name and
flags from 'cat /proc/cpuinfo' to identify the capabilities of your CPU,
including whether it is in fact a 64-bit CPU in 32-bit mode.

> There are some different entiries at grub. And what to do if i want to
> install and run an application given as 32 bit , on my 64 bit system?

A Linux system is installed as either 32-bit or 64-bit.  If grub lists
both 32-bit and 64-bit environments, you must be sure that the boot/root
environment is correct for each entry, because you can't mix 32-bit core
software (init, modules, shells etc) with a 64-bit kernel, and vice
versa.  Each entry in the grub menu specifies three things that must all
have the same architecture (ie , all must be 32-bit, or all must be
64-bit):
1: Kernel
2: initrd (initial ramdisk)
3: system binaries on the root disk

There are other factors that need to be considered, but these are the
key ones.  If we know more about the grub entries, we might be able to
offer better advice.


If you are running in 64-bit mode, you can install and run 32-bit
applications.  The Ubuntu developers package a set of libraries that
supply 32-bit versions of the standard system and library functions, in
package ia32-libs, so that most 32-bit applications can run properly.
If the 32-bit software has been correctly packaged for 64-bit Ubuntu, it
will list the 32-bit compatibility packages that it requires, as
dependencies that will be installed - they will be listed by apt-get
under the heading
    'The following extra packages will be installed'



 
> 
> Regards
> 
-- 
Tim Frost <timfrost at xtra.co.nz>
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