switching from 32-bit to 64-bit

[bogstad-e+AXbWqSrlAAvxtiuMwx3w at public.gmane.org (Bill Bogstad)]

On Thu, Jul 29, 2010 at 5:15 PM, Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org> wrote:
> On 07/29/2010 11:27 AM, Dan Ritter wrote:
>> On Thu, Jul 29, 2010 at 10:12:01AM -0400, Seth Gordon wrote:
>>
>>> I have a desktop machine at home that used to run 64-bit Ubuntu. ?Then
>>> the hard drive went south, so I got a fresh drive, bought an Ubuntu
>>> CD-ROM from the Micro Center, did a fresh install from the CD-ROM, and
>>> then upgraded over the network to the then-latest version.
>>>
>>> At some point I noticed that I was running the 32-bit version of the OS,
>>> not 64-bit. ?Is there a relatively painless way to move everything over?
>>> ? (I need to upgrade it from 9.10 to 10.04, in any event.)
>>>
>> Nope. Unlike switching kernels, x86-32 to x86-64 is a complete
>> architecture change.
>>
>> There is no in-place upgrade. Your best bet is to add a disk,
>> install 64-bit on that, test things, and move data over.
>>
>>
> You can theoretically do this, but it is a very big job and very easy to
> screw things up.
> (1) filesystem (not 100% sure here).

This is generally not a problem.

> (2) kernel
> (3) kernel modules - modules are coordinated with the kernel.

3(a) initial ramdisk

> (4) libraries. /lib, /lib32, /usr/lib,/usr/lib32, /lib64 /usr/lib64
> (64-bit libs are symlinked to lib).
> (5) commands although most 32-bit commands will work in a 64-bit
> environment.
> (6) stuff I forgot :-)

System config in /etc....

> If you create another partition with your home directory, possibly
> /usr/local, and possibly some of your downloaded applications you are
> preserving most of the stuff you added, then you can do a clean install
> by reformatting the boot and root partitions.

If you are running a machine as a local server, you might have DHCP,
DNS, NTP, and NFS configs to migrate as well.

Bill Bogstad