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I am about to upgrade my system from a sub-Gigahertz Duron to a Athlon 64
3000+. I would like to run in 64-bit mode, but I don't want to do a
complete re-install. I have taken a lot of time to get my system
configured and working nicely, so a re-install from scratch would not be
pleasant.

Can I just adjust the settings in /etc/make.conf and change the profile
and let it convert to 64-bit over time (as packages are updated)?

If the 64-bit conversion is not practical, currently (for historical
reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
have "-march=athlon"), how should I convert to a more appropriate
CHOST?

Whoever wrote:
> I am about to upgrade my system from a sub-Gigahertz Duron to a Athlon
> 64 3000+. I would like to run in 64-bit mode, but I don't want to do a
> complete re-install. I have taken a lot of time to get my system
> configured and working nicely, so a re-install from scratch would not be
> pleasant.
>
> Can I just adjust the settings in /etc/make.conf and change the profile
> and let it convert to 64-bit over time (as packages are updated)?

No, but you can continue to use it as 32-bit.


> If the 64-bit conversion is not practical, currently (for historical
> reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
> have "-march=athlon"), how should I convert to a more appropriate CHOST?

That setup isn't a good one for a Duron, you should have had
CHOST=i686-pc-linux-gnu, but switching CHOST ain't safe, so you are more or
less stuck with that i586-pc-linux-gnu.

--

//Aho

Whoever wrote:

> I am about to upgrade my system from a sub-Gigahertz Duron to a Athlon
> 64 3000+. I would like to run in 64-bit mode, but I don't want to do a
> complete re-install. I have taken a lot of time to get my system
> configured and working nicely, so a re-install from scratch would not
> be pleasant.

Actually, it's probably not as unpleasant as it may seem. All the
configurations related to the Gentoo part should be more or less in
/etc/, and most can be copied directly and tweaked for the new system.
To reinstall everything you already had, just grab the world file from
the old system.

I did this once to a system where the MB died and I had to switch it
into a CPU incompatible box. I booted a Knoppix and installed the
system in a chrooted folder in the old file system, with most of the
same configuration files, and then finished up by moving around the
relevant folders to their new homes.

> Can I just adjust the settings in /etc/make.conf and change the
> profile and let it convert to 64-bit over time (as packages are
> updated)?

Mixed 32 and 64 bit systems should be technically possible, but I think
this is something one needs to prepare from the beginning if one wishes
a less painful process.

> If the 64-bit conversion is not practical, currently (for historical
> reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
> have "-march=athlon"), how should I convert to a more appropriate
> CHOST?

CHOST conversions are generally not recommended, IIRC. It should be
possible, but it might be easier to start from scratch. Might also be a
good chance to clean out the accumulated gunk (if one is not good at
keeping a clean Gentoo system).

--
PeKaJe

There is a new service pack that fixes all of IIS's problems
permanently. Go here to download it: http://www.apache.org

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

| ----- Original Message -----
| From: Whoever <nobody@devnull.none>
| Sent: 12/12/2006 2:36:58 AM +0100
| Subject: Converting to 64-bit
|

| If the 64-bit conversion is not practical, currently (for historical
| reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
| have "-march=athlon"), how should I convert to a more appropriate CHOST?

If you're really serious about changing the CHOST, you may (or may not)
find something helpful about it at
http://www.gentoo.org/doc/en/change-chost.xml.
Converting to amd64 over time looks difficult to me, because running 32
and 64-bit programms at the same time is impossible.
I myself use a amd64 profile with multilib support, so I can run 32-bit
and 64-bit binaries. But: it is necessary, that EVERY library a 32-bit
binary needs, is available under /lib32/ or /usr/lib32/. 32-bit binaries
only work with 32-bit libraries, as 64-bit binaries only load 64-bit
libraries.
So it looks rather impossible to me to convert to 64-bit "over time".

Good luck,

- --
*Sebastian Volke*
registered Linux user #426550

mail address: echo ozslxhmfw_gfxyn@lrc.sjy | perl -pe 'y/a-z/v-za-w/'
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On Thu, 14 Dec 2006, Sebastian Volke wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> | ----- Original Message -----
> | From: Whoever <nobody@devnull.none>
> | Sent: 12/12/2006 2:36:58 AM +0100
> | Subject: Converting to 64-bit
> |
>
> | If the 64-bit conversion is not practical, currently (for historical
> | reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
> | have "-march=athlon"), how should I convert to a more appropriate CHOST?
>
> If you're really serious about changing the CHOST, you may (or may not)
> find something helpful about it at
> http://www.gentoo.org/doc/en/change-chost.xml.

I found that after posting. I should have looked for it: one of Gentoo's
greatest assets is its documentation on setting up, configuring and
tweaking the system.

> Converting to amd64 over time looks difficult to me, because running 32
> and 64-bit programms at the same time is impossible.
> I myself use a amd64 profile with multilib support, so I can run 32-bit
> and 64-bit binaries. But: it is necessary, that EVERY library a 32-bit
> binary needs, is available under /lib32/ or /usr/lib32/. 32-bit binaries
> only work with 32-bit libraries, as 64-bit binaries only load 64-bit
> libraries.
> So it looks rather impossible to me to convert to 64-bit "over time".

Thanks for this. I guess that I will just run a 64-bit kernel and then
build up a new installation in a chroot jail.

On Thu, 14 Dec 2006, Sebastian Volke wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> | ----- Original Message -----
> | From: Whoever <nobody@devnull.none>
> | Sent: 12/12/2006 2:36:58 AM +0100
> | Subject: Converting to 64-bit
> |
>
> | If the 64-bit conversion is not practical, currently (for historical
> | reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
> | have "-march=athlon"), how should I convert to a more appropriate CHOST?
>
> If you're really serious about changing the CHOST, you may (or may not)
> find something helpful about it at
> http://www.gentoo.org/doc/en/change-chost.xml.
> Converting to amd64 over time looks difficult to me, because running 32
> and 64-bit programms at the same time is impossible.
> I myself use a amd64 profile with multilib support, so I can run 32-bit
> and 64-bit binaries. But: it is necessary, that EVERY library a 32-bit
> binary needs, is available under /lib32/ or /usr/lib32/. 32-bit binaries
> only work with 32-bit libraries, as 64-bit binaries only load 64-bit
> libraries.
> So it looks rather impossible to me to convert to 64-bit "over time".

I started to try to build a new 64-bit system in a chroot environment,
but have run into a problem:
chroot: cannot run command `/bin/bash': Exec format error

I assume that this is because the kernel doesn't recognise 64-bit
binaries. I have previously selected Opteron/Athlon64 for my processor
sub-architecture and rebuilt the kernel and rebooted. Yet uname still
shows it as i686:

# uname -a
Linux newhome 2.6.18-gentoo-r264b #4 SMP PREEMPT Sat Dec 16 18:17:06 PST
2006 i686 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux

Is there anything else I need to do in order to get the system to
chroot into my 64-bit environment? Or is this approach not going to work?

Whoever wrote:
>
>
> On Thu, 14 Dec 2006, Sebastian Volke wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> | ----- Original Message -----
>> | From: Whoever <nobody@devnull.none>
>> | Sent: 12/12/2006 2:36:58 AM +0100
>> | Subject: Converting to 64-bit
>> |
>> | If the 64-bit conversion is not practical, currently (for historical
>> | reasons), I have been using "CHOST=i586-pc-linux-gnu" (although I also
>> | have "-march=athlon"), how should I convert to a more appropriate
>> CHOST?
>>
>> If you're really serious about changing the CHOST, you may (or may not)
>> find something helpful about it at
>> http://www.gentoo.org/doc/en/change-chost.xml.
>> Converting to amd64 over time looks difficult to me, because running 32
>> and 64-bit programms at the same time is impossible.
>> I myself use a amd64 profile with multilib support, so I can run 32-bit
>> and 64-bit binaries. But: it is necessary, that EVERY library a 32-bit
>> binary needs, is available under /lib32/ or /usr/lib32/. 32-bit binaries
>> only work with 32-bit libraries, as 64-bit binaries only load 64-bit
>> libraries.
>> So it looks rather impossible to me to convert to 64-bit "over time".
>
> I started to try to build a new 64-bit system in a chroot environment,
> but have run into a problem:
> chroot: cannot run command `/bin/bash': Exec format error

The 32bit kernel do not have any 64bit support, so you can't run 64bit
programs without using an emulator, not sure if qemu can help you here.


> I assume that this is because the kernel doesn't recognise 64-bit
> binaries. I have previously selected Opteron/Athlon64 for my processor
> sub-architecture and rebuilt the kernel and rebooted. Yet uname still
> shows it as i686:

You can build a 64bit kernel with support for 32bit, this may work.
On Sparcs you use 64bit kernel with a 32bit userspace, as you don't gain
anything really using 64bit for quite standard systems (on heavy calculating
systems you would).


--

//Aho

On Sunday 17 December 2006 10:50, J.O. Aho stood up and addressed the masses
in /alt.os.linux.gentoo/ as follows...:

> Whoever wrote:
>
>> I started to try to build a new 64-bit system in a chroot environment,
>> but have run into a problem:
>> chroot: cannot run command `/bin/bash': Exec format error
>
> The 32bit kernel do not have any 64bit support, so you can't run 64bit
> programs without using an emulator, not sure if qemu can help you here.

It can't. ;-) While it is possible to emulate a 32-bit system on a 64-bit
architecture via /qemu/ - although if the OS is the same, the /x86_64/
architecture can run 32-bit code natively in a 64-bit environment without
the need for an emulator - it is to my knowledge (and at the moment) not
possible to run a 64-bit emulator on a 32-bit system.

>> I assume that this is because the kernel doesn't recognise 64-bit
>> binaries. I have previously selected Opteron/Athlon64 for my processor
>> sub-architecture and rebuilt the kernel and rebooted. Yet uname still
>> shows it as i686:
>
> You can build a 64bit kernel with support for 32bit, this may work.
> On Sparcs you use 64bit kernel with a 32bit userspace, as you don't gain
> anything really using 64bit for quite standard systems (on heavy
> calculating systems you would).

It also deserves to be noted that choosing Athlon64/Opteron as the processor
type in the kernel configuration tool will not normally build a 64-bit
kernel. It will just be a 32-bit kernel with optimizations for the
specified processor.

You need the cross-compiler version of /gcc/ and of the GNU /make/ utilities
to be able to generate a 64-bit kernel. Even if you select
Athlon64/Opteron (or EM64T for that matter) from the kernel configurator,
the /.config/ file will still be set for /x86,/ not for /x86_64./

--
With kind regards,

*Aragorn*
(registered GNU/Linux user #223157)

Aragorn wrote:
> On Sunday 17 December 2006 10:50, J.O. Aho stood up and addressed the masses
> in /alt.os.linux.gentoo/ as follows...:
>
>> Whoever wrote:
>>
>>> I started to try to build a new 64-bit system in a chroot environment,
>>> but have run into a problem:
>>> chroot: cannot run command `/bin/bash': Exec format error
>>
>> The 32bit kernel do not have any 64bit support, so you can't run 64bit
>> programs without using an emulator, not sure if qemu can help you here.
>
> It can't. ;-) While it is possible to emulate a 32-bit system on a 64-bit
> architecture via /qemu/ - although if the OS is the same, the /x86_64/
> architecture can run 32-bit code natively in a 64-bit environment without
> the need for an emulator - it is to my knowledge (and at the moment) not
> possible to run a 64-bit emulator on a 32-bit system.

It is possible, I just tried it:

qemu-system-x86_64 -boot d -cdrom crux-x86_64-2.1.iso

According to the qemu status page
http://fabrice.bellard.free.fr/qemu/status.html x86_64 on x86 is
working in system emulation mode "only", but not in user emulation mode.

With system emulation you can boot a complete system. With user
emulation, you could run standalone 64 bit executables, see e.g.
http://kidsquid.com/cgi-bin/moin.cgi/UserModeEmulation

Regards...
Michael