[lfs-support] Understanding 32bit vs 64bit and multilib systems

Bruce Dubbs bruce.dubbs at gmail.com
Mon Nov 26 21:11:15 PST 2012

Kyle Brennan wrote:
> Hi,
> I'm not sure that this is the right mailing list, but I'm going to throw
> this out there anyways.
> I've got a few questions about building LFS on a 64 bit host and how
> multilib works.
> 1. What exactly is multilib?  (I've googled, wikipedia'd etc and I'm still a
> bit confused) from my understanding, it's simply an additional set of
> libraries that will allow for a system to interpret both 32 bit and 64 bit
> machine code.

That's right.

> 2. I'm building on a 64 bit system, if I follow the book exactly, would this
> build yield a 32 bit or 64 bit system?

It actually depends on the host OS.  If the host OS is 32-bit, the new 
one will be "pure" 32-bit.  If it's 64-bit, the new one will be a "pure" 
64-bit system.  To make a multi-lib system, you have to compile the 
libraries needed twice with different parameters.  We don't do that in 
LFS.  You also don't need the "other" size libraries if you have the 
source.  You only need them if running a proprietary 32-bit binary on a 
64-bit system.

> 3. if the answer to question one is 64 bit, is this automatically a multilib
> system or are there additional steps that will pave the way to multilib?
> 4. can I use the LFS book to create a 32bit system on a 64 bit OS?  (I'm
> assuming that the book for this would be CLFS though)

See above.

   -- Bruce

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