More glibc's

Greg Schafer gschafer at zip.com.au
Wed Nov 26 02:45:42 PST 2003


On Tue, Nov 25, 2003 at 08:59:40PM -0700, Kevin P. Fleming wrote:
> One technique that can frequently be used for this is to use
> 
> LD_ASSUME_KERNEL=2.2.5
> 
> which makes glibc think it's running on an old system and it does a 
> better job of emulating the previous glibc releases. Won't always work, 
> but it's cheap to try.

Kevin, that technique only works on a RH system. Setting that variable on an
LFS system doesn't do much at all.

Essentially, what they do is install separate libc's in different paths
e.g. /lib/tls, /lib/i686 and so forth. By setting that variable, they can
control which libc gets loaded at runtime. Debian have just started doing it
too.

I've studied the Glibc sources to try and figure out how it works. It's
really quite clever and fascinating and worth looking into if you're
interested. Grep for "hwcap". It's also worth studying the RH spec file. The
"--enable-kernel=" switch plays a role. Overall, the technique is very
useful for distros, not much use for LFS.



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