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Re: partitioning with dualboot 32 / 64

On Mon, Nov 13, 2006 at 03:22:00PM +0100, Micha wrote:
> I'm going to install debian etch on AMD64 debian, from scratch on a
> clean HD, and i intend to prepare partitions for an additional x32
> install which i may decide to add later, depending on my experiences,
> just as a fallback. I will use the same apps, and both would be Debian
> Sid, updated daily or right after booting. 
> I like to hear your opinion if that's worth the effort, and if i should
> try to balance redundancy and maintenance costs ? 

I would think it was much better to just install the 64bit and then
install a 32bit in a chroot.  That keeps both available at the same time
(since a 64bit kernel will run both).

> The first consideration is, in how far would a debian sid x64
> installation differ from the analog x32 install at all ? Can i track it
> down to some few directories, like /bin,  /sbin,  /lib ... what else? 
> Then i would ask if it's possible to boot into the same 'stub' root
> system (if we can call it still that) and mount the missing directories
> according to the chosen kernel - via initrd, and maybe some custom
> script. Possible ? Impossible ? Useless ? I've no idea.

The installs are very similar.  

> Traditionally, however, i would see it the other way round, booting 
> into a dedicated root and mounting some shared directories.
> Then i have some questions:
> /home .... can there still be differences e.g. in version between x64
> and x32 ?

Sharing /home sounds perfectly reasonable.  Of course if the use has any
binaries compiled for 64bit they won't run with a 32bit kernel, and
32bit programs may require libraries that aren't on a 64bit system.

> /var/cache/apt/archives  ... i can't see any problem here, can you ?

Not sure.  Of course anyone that does an apt-get clean after an upgrade,
won't have anything in there anyhow.

> /usr/share .... a relatively huge peice - but will apt refuse to manage
> (mainly, to deinstall) stuff  that was updated by the 'other debian' ?
> (Would at least /usr/share/doc be safe ?)

I don't think dpkg will like that idea at all.

> /usr/scr .... i will have several source trees from kernel.org or
> debian, and i've no problem with backups of different .configs, so
> basically this should work...? 

Your sources you can do whatever you want.  Since dpkg does install some
things to /usr/src, it is not a good place to keep your own sources.
Pick a better location (like /home for example).

> I think i can share swap (with an additional hibernation swap for each
> debian.)

I don't know if the swap format is identical between architectures.  You
would have to find that out first.

> I discarded the idea to share /tmp, don't want to fix the size.
> I also think i will use tmpfs.

/tmp is often better done as tmpfs in ram anyhow.

Len Sorensen

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