In the past, I've deployed new 64 bit systems and I've worked on and developed on 64 bit systems.

But until a week ago, my workstation was a 32 bit system.

Now, it is a 64 bit quad core Phenom II system, and I suppose I need to start the migration to 64 bit Linux.

I do not want to blow off my system and rebuild it. Many reasons, but suffice it to say that it will ultimately be far easier on me if I don't start over. This particular system dates back a decade and through many many updates. There is some digital debris in it, but there is also a fair amount of customization that I have implemented either for my own purposes or for customers, and to lose that customization would represent a headache for me.

What I want to do is install a 64 bit system over top of the 32 bit system. It is my hope that doing this would install the necessary 64 bit libraries, while not impacting the existing 32 bit libraries (except with some possible symlink problems). I then, hopefully, could boot into a 64 bit kernel while still running 32 bit programs.

Is this feasible?

My backup system is comprehensive; I COULD just try it and back up if my system became hosed. But I'd rather not; I have a lot of work to do and I'd rather not learn by doing in this case.

Does anyone here know if this will work, or - as importantly - does anyone here know that this will NOT work?

What KIND of Linux are you running?

As far as I know, no, you can't just upgrade from 32-bit to 64-bit. I tried it with RHEL and while it seemed to work, once it came time to upgrade the system to the next patch level, it would have been easier to do a fresh install.

Back up your data, do a fresh install of 64-bit, then restore data piecemeal.

I did find this link that might be helpful. I don't think it's totally impossible. But maybe try this guys approach and clone your system into a virtual machine, then try cross-grading the VM.

http://www.linux.com/archive/feature/123800

I've always found it best to do a major upgrade in concert with installing a new disk drive. How old is your boot drive? Several years old? In fact, I just upgraded to 64bit Debian this week after I got a new 1TB drive. Something to consider.

Yeah, I had found that link. Might even go the way he did. I have Mandriva and not Fedora, but those two are very close architecturally.

Also as I look further I find lots of "gotchas" to 64 bit desktop workstations. I have used 64 bit mostly on servers and embedded systems. I haven't tried it on a desktop system.

Might be best to just wait awhile until the 64 bit software is more mature. I've compiled a 32 bit kernel that will address 64 gigs of RAM, and I might just start using that - if there isn't a performance hit for doing it. I read a review of a Ubuntu kernel that showed basically no impact when compiled to address 64 Gigs of RAM, compared to the "stock" kernel that was compiled for up to 4 Gigs, so maybe it is OK.

Actually, this system hard drive is a shade over a month old. And was a replacement for another drive that lasted three months. Which was a replacement for a drive that lasted two days.

Which was a replacement for an old drive that was starting to report lots of bad blocks.

I have to say I've gotten real tired of recovering my system in the recent past.

The oldest drive was an IBM 10K RPM SCSI-320 LVD Ultrastar that I managed to drop on a concrete floor. It ran for quite awhile after that, but it never sounded the same and then began to fail. The first replacement was a Hitachi 15K RPM Ultra-320 SCSI. The second replacement was also a Hitachi, provided by the same dealer.

The most recent replacement is a Fujitsu 15K RPM Ultra-320 drive.

I'm in no real rush to migrate to 64 bit, and I really really don't want to blow off the system. Since /home is on a different drive than the system (there are 5 internal SCSI drives in this system), I can undoubtedly keep all my settings, but I just have this thing about starting over.

How are you doing with things like flashplayer on your 64 bit distro? How much have you run across that won't work?

I'm concerned about a number of things, particularly VMWare Workstation. I have that in a 32 bit version and would like to continue running it. If I upgrade that to 64 bit, then will I have issues running 32 bit virtual machines?

There really are a lot of questions I have to answer before I make the move. Maybe I'll configure for a dual boot for awhile. Hmmm... That might be a good choice.

Well, that is described below my handle. Beyond that, if it can be accomplished with one distro it can probably be accomplished with others.

There are a large number of issues here that I have to know the answer to before I begin because this is a production machine and if I hose it, I'll have to roll back rather than keep trying to sort it out.

I ran across that one fellow who did Fedora the way I want to do it, and I might follow his lead; Fedora and Mandriva are very similar.

I'm also interested in feedback about how well 64 bit is supported for desktops these days. I do know that I have to be quite careful with code that I write that I want to compile on both architectures; they are NOT the same, and I don't know how widely 64 bit is being supported at this time. I'm doing it (supporting 64 bit) because one client wants me to, and I've been doing my 64 bit compiles using SSH and his server.

Unless I'm looking in the wrong place, you listed three for a question that deserved a specific one.

I can think of several reasons that this task would be harder/different in any Debian based distribution than it would be in Fedora.

The link posted earlier in this thread about someone doing this to Fedora educated me about a bunch of things I hadn't thought through that make this harder in Fedora than I would have guessed. But none of that shifted my opinion that it would be even harder in Debian than in Fedora.

You listed Kubuntu, so if that were the system you want to try, you might be in for even more difficulty than you expect.

Your later post implies it is the Mandriva system you want to convert. I don't know how Mandriva would compare on that criteria.

Meaning what?

Very little open source still has portability bugs that manifest when compiled for x86_64. I'm running 64 bit Mepis on my home system and notice no problems.

I'm used to working with code that had to be portable to 64 bit Sun systems long before it needed to be portable to x86_64. So being careful about that sort of thing has always just been a part of programming.

Browsing is an issue that I haven't completely resolved. I can't get Firefox 3.6 to work properly. There's an appearance issue that probably corresponds to the gtk complaints I'm getting. OTOH, the IceWeasel that comes with Debian works just fine. I'm using the 64 bit beta flashplayer, and that seems OK so far - at least I can watch the youtubes of my granddaughter just fine.

I can't tell you about VMWare, but 64-bit VirtualBox seems to work with the 32-bit XP client OS I have.

I have a number of Wine apps for Ham Radio, and they're all working OK.

TBH, my biggest complaint at this point is that the card deck for the gnome solitaire games seems to be different, so I need to boot up 32-bit and track that down. In fact, having the 32-bit still running on the old disk has been a real help in figuring out things that weren't part of my desktop configuration. As an example, I had to go back to 32-bit to figure out which thermal monitoring module I needed to enable.

If your package manager allows you to save your package list and restore it, be sure and do that. Don't forget networking configs, either. And just go ahead and install ia32-libs and be done with it.

If you use a custom kernel, you have some messing with the config to do. I'd suggest that you copy over the /boot/config-`uname -r` and run "make oldconfig" first, then put your custom stuff back in, maybe with the help of "diff".

It hasn't been that bad, I guess, but it has taken me a lot of time.

Full backup; fresh install. Don't risk it.

I ran 64-bit Debian on my laptop for some time with no specific issues. Flash and Java worked great -- in Opera, too.

One more thing about 64-bit flashplayer and firefox: I downloaded the source for Firefox Minefield/3.7a3pre, compiled it, and that's what I'm running now, along with 64-bit flashplayer. No problems after a couple of days now.