How to let Linux run 64-bit mode Only

[Ross]

Hi there,
I have an AMD Opteron machine running Red Hat Enterprise Linux (RHEL)
version 3 Update 2 which supports both
64-bit mode and 32-bit mode.
The question is: How can I force the system to run 64-bit mode only?

My company has a software product which runs well in 32-bit mode. When I run
it on the AMD Opteron machine, it will automatically run in 32-bit mode
because this machine is downgrade compatible. But I'd like to test my
software in 64-bit mode.
Is there a parameter I could change, or could I compile the kernel to force
it to run in 64-bit only?
Thanks in advance,
Ross

 

[Marcin =?ISO-8859-2?Q?D=EAbicki?=]

Ross kiedys napisal:

Hi there,
I have an AMD Opteron machine running Red Hat Enterprise Linux (RHEL)
version 3 Update 2 which supports both
64-bit mode and 32-bit mode.
The question is: How can I force the system to run 64-bit mode only?

My company has a software product which runs well in 32-bit mode. When I
run it on the AMD Opteron machine, it will automatically run in 32-bit
mode because this machine is downgrade compatible. But I'd like to test my
software in 64-bit mode.
Is there a parameter I could change, or could I compile the kernel to
force it to run in 64-bit only?
Thanks in advance,
Ross

If you have support for both 64 and 32 bit modes then you are booting real
64 bit system. In software meaning mode is nothing more but set of
libraries to run old applications. 64 bit Linux by default uses 64 but if
youhave system inside system installation for backward compatibility, you
have also 32bit libs. The situation is almost the same if you have
multiarch. In both situations usually when you are trying to run an
application, system is checking if it is 32bit application and if it is
then it uses 32bit libs only for this application. If it isn't then system
uses 64bit versions. Of course all this things work if you have running
64bit kernel and if you have installed right libraries

 

[Wes Newell]

Hi there,
I have an AMD Opteron machine running Red Hat Enterprise Linux (RHEL)
version 3 Update 2 which supports both
64-bit mode and 32-bit mode.
The question is: How can I force the system to run 64-bit mode only?

Load a 64bit kernel and only run 64bit software.

My company has a software product which runs well in 32-bit mode. When I
run it on the AMD Opteron machine, it will automatically run in 32-bit
mode because this machine is downgrade compatible. But I'd like to test
my software in 64-bit mode.

Then you'll have to compile it in 64bit mode.

Is there a parameter I could change, or could I compile the kernel to
force it to run in 64-bit only?

I'm pretty sure a 64bit kernel won't run on a 32 bit machine, but you can
run a 32bit kernel on a 32bit compatible 64 bit cpu. Load a 64 bit kernel,
then load a 64bit compiled version of your software. That should do it,
but that version wouldn't run on a 32 bit kernel unless you put hooks in
your software to check and act according to what OS is loaded.

 

[Randy Howard]

Hi there,
I have an AMD Opteron machine running Red Hat Enterprise Linux (RHEL)
version 3 Update 2 which supports both
64-bit mode and 32-bit mode.
The question is: How can I force the system to run 64-bit mode only?

If you're feeling real brave, build a cron job to run every 10
minutes or so to run a script that does something along the lines of
this:

find / -type f | xargs file | grep "ELF 32" | cut -c1-30 |
tr ':' ' ' | xargs rm -f

Untested (for obvious reasons) and almost certainly not robust.

If you figure out what that does, finding a better way should be easy
enough.

[don't take the above seriously, you'll really regret it if you do]

My company has a software product which runs well in 32-bit mode.

Then run it on your Opteron system. It should be happy with it.

When I run it on the AMD Opteron machine, it will automatically run
in 32-bit mode because this machine is downgrade compatible.

You mean it supports 32-bit binaries. Most people think that's a
good thing.

But I'd like to test my software in 64-bit mode.

Then compile a 64-bit version of it, remove the 32-bit version and
install the 64-bit version. Or, simply run the 64-bit version from
a different directory, or give it a different name. Example, the
program is called "mysoft". Call the 64-bit one "mysoft64". Now
you can run them both at the same time if you like.

Is there a parameter I could change, or could I compile the kernel to force
it to run in 64-bit only?

You don't need to.