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migrating from x86 to x86_64 using LiveCD and chroot
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ferg
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PostPosted: Wed Jun 27, 2007 12:18 pm    Post subject: migrating from x86 to x86_64 using LiveCD and chroot Reply with quote

Hi all,

I've recently upgraded my motherboard and CPUs to a Nocona EM64T board with 6Gb Ram.

I know it's impossible to migrate to x86_64 using a live system, but I'm looking into the possibilities of booting from the appropriate LiveCD, chroot'ing into my system, and migrating it from there. Has anybody done this succesfully?

A second related question is running a 32bit system with a 64bit kernel. Anybody done this? I saw this post about it from 2005. Has anything changed?

https://forums.gentoo.org/viewtopic-t-405255-highlight-profile+em64t.html?sid=95320fd3b7d3c5ceb4849a9972330ead

If I could boot from a 64 bit kernel, then I could copy my live filesystem to another partition and then create a chroot of this. Then I think I could gradually migrate this to 64bit? Feasible or am I talking gibberish?

Another stupider alternative is to install a new AMD64 bit Gentoo into a Chrooted filesystem (with 64 bit kernel). I could then do another chroot into a duplicate copy of my main filesystem, and compile all this for AMD64. so a 64 Chroot in a 64bit Chroot, running on a 32bit system, but running a 64bit kernel. wow!

I guess it might be quicker to start from scratch. However, I've had this system running since Dec 2002, and I'd hate to have to start from scratch again (yes I have lots of backups!!).

Cheers
Ferg
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ferg
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PostPosted: Thu Jun 28, 2007 12:20 pm    Post subject: Using a 64bit kernel with a 32bit OS Reply with quote

Hi all,

is anybody running a 32bit system with a 64bit kernel. I saw this post about it from 2005. Has anything changed?

https://forums.gentoo.org/viewtopic-t-405255-highlight-profile+em64t.html?sid=95320fd3b7d3c5ceb4849a9972330ead

This is in part due to an idea I have about migrating to AMD64. If I could boot from a 64 bit kernel, then I could copy my live filesystem to another partition and then create a chroot of this. Then I think I could gradually migrate this to 64bit? (I posted this as part of another question I had earlier).

Cheers
Ferg
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Rob1n
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PostPosted: Thu Jun 28, 2007 1:14 pm    Post subject: Reply with quote

I don't think you can combine things like that, no. However, the general idea works okay:

  • Boot from an x86-64 CD/DVD.
  • Copy the existing filesystem to another partition (you couldn't safely do this with a live filesystem anyway).
  • Install new x86-64 filesystem.
  • Mount the old filesystem, chroot & run any 32-bit apps needed.


This is the process I followed when I upgraded my system last year (after a hardware failure).
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ferg
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PostPosted: Thu Jun 28, 2007 1:30 pm    Post subject: Reply with quote

Hi,

thanks for responding. That sounds quite feasible.

Do you think I could install a real minimal system, and use this to recompile my chroot'ed old filesystem for x86_64?

Or perhaps I should just start from scratch. This system was first installed in dec 2002, and there must be a lot of crud left over in there!!

Cheers
Ferg
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depontius
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PostPosted: Thu Jun 28, 2007 1:57 pm    Post subject: Reply with quote

I ran a mostly-32-bit userspace on a 64-bit kernel for a while. What I really did was run a 32-bit chrooted xdm. So all of my init services were 64-bit, but I tweaked the xdm script so that under direction a flag in /etc/conf.d/xdm it could either start in 64-bit or linux32/chroot into 32-bit. That way users' sessions would be entirely 32-bit.

I did this to get around the numerous 32/64-bit problems when my wife was trying to view web content.

Then a while back, there was some sort of update to xdm, and I lost my changes. The scripts were different enough that it wasn't straightforward to port my old fixes forward, so for the time being I left xdm and users' sessions running 64-bit. Nobody complained, and in fact it appears that other updates to 64-bit userspace while we were running 32-bit userspace took care of most of our problems.

So today we're still running 64-bit xdm and userspace.
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Rob1n
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PostPosted: Thu Jun 28, 2007 2:01 pm    Post subject: Reply with quote

I'd recommend starting from scratch, otherwise you'll have to go through everything afterwards and make sure there's no stray 32-bit applications/libraries left. There's also some data files (e.g. database files) that I wouldn't count on being compatible between 32-bit and 64-bit versions.

You can use the old /var/lib/portage/world as a starting point but you may well find some of the applications aren't classed as stable on x86_64. In this case you'll have to either unmask these or look for alternatives.

Once you've got everything reinstalled then you can look at comparing config/data directories (most of these should be just a case of copying the old files back over), leaving the old filesystems around until you're happy everything's transferred okay.
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nixnut
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PostPosted: Thu Jun 28, 2007 6:13 pm    Post subject: Reply with quote

Moved from Installing Gentoo to Duplicate Threads.
See https://forums.gentoo.org/viewtopic-p-4069925.html#4069925 for some answers.
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