Advice for "crossgrading" from 32 bit F11 to x64 ?

[Sam Varshavchik]

Linuxguy123 writes:

> I do a lot of photo processing... things like generating 200 jpgs from
> raw files at one go.   My laptop has 4GB of RAM but is currently only
> using 3GB because I am running a 32 bit kernel. 

Why led you to this conclusion? 32 bit Linux is perfectly capable of 
addressing 4 GB+ of RAM. You need to install a PAE kernel, which should 
already be the case, by default.

If you are not already booting a PAE kernel, just install it.

> Sooner or later I want to upgrade to a 64 bit kernel and 8 GB of RAM.
> Other than this article, I can't find any information on the subject.
> 
> http://www.linux.com/archive/feature/123800
> 
> I am looking to do the upgrade WITHOUT reinstalling Fedora.  I've done

Someone who has sufficient technical experience and know-how might be able 
to pull this off. But, to be perfectly straight, if you have to ask how to 
do this, you do not have the requisite know how.

Here's what needs to be done, and you judge for yourself if you think you'll 
be able to handle something like this:

1) force-install a 64-bit kernel, 64 bit glibc, and 64 bit init. I'm pretty 
sure that the 32 bit mkinitrd will barf when it tries to assemble an initrd 
for the 64 bit kernel. You'll have to unpack your current mkinitrd, look 
inside, enumerate all the modules that it loads, than manually build an 
equivalent 64 bit initrd, with the analogous kernel modules. Cross your 
fingers, and attempt to boot the new kernel into single user mode.

2) Proceed to replace your RPMs with their corresponding 64 bit versions, by 
hand. I'm rather skeptical that "yum upgrade" will figure it out 
automatically. More than likely, neither yum nor rpm will have any idea how 
to do this. This will have to be spoon fed. You'll have to identify what all 
the dependencies are, between various packages, and update/convert them in 
the right order.

All the time, have a rescue disk available in case some detail gets missed, 
and you end up with an unbootable brick. Plus, the know-how to to boot a 
rescue disk, mount your partitions, and unfix whatever you fixed that broke 
everything.

Not to mention the task of figuring out how to suck in the new 64 bit 
packages into the system, from single-user mode. I suppose that you can 
either burn them to a DVD beforehand (slow!), or pull them in over the 
network, in which case you'll need to know how to bring up networking from 
single-user mode, and figure out the exact list of packages to upgrade, at 
once, in order to convert all packages that support networking from 32 to 64 
bits, at once, so that you can reestablish network connectivty after cutting 
over to 64 bit packages, for that part.

> enough re installations in the past to know that I don't want to go
> there.

As best as a reinstall is, I'd rather do that, then try this kind of a 
cross-grade. Even though I believe I can pull it off, myself.

But, if all you want is more RAM, all you really need is the PAE kernel, 
which I believe can handle up to 16 GB. A single 32 bit process is still 
limited to accessing 3 GB max, but overall the system will be able to use up 
to 16 gigs. If that works out for you, this is your path of least 
resistance.

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