Minimum Host Prerequisites

Ken Moffat ken at linuxfromscratch.org
Mon Oct 20 11:31:43 PDT 2008


On Mon, Oct 20, 2008 at 07:24:50PM +0200, Gilles Espinasse wrote:
> Selon Ken Moffat <ken at linuxfromscratch.org>:
> ...
> 
> LFS dev has on glibc --enable-kernel=2.6.0
> FC9 has set --enable-kernel=2.6.9
> Debian lenny has set --enable-kernel=2.6.18
> Greg has the same 2.6.18 setting on glibc chroot compilation (but nothing on
> first compilation).
> 
> It does not look clear to me if the reason for debian to set 2.6.18 are valid
> "...Currently, MIN_KERNEL_SUPPORTED is set to 2.6.9 and (as you know)
> leaves out some newer features.
> ..."
> 
> My understanding was that more compatibility workaround were enabled with a
> lower --enable-kernel, not that it disable some new features. I may have been
> partially wrong, reading glibc manual:
> "The higher the version number is, the less compatibility code is added, and the
> faster the code gets."
> 
> On IPCop, we had choosen --enable-kernel=2.6.5 because of a reference I can no
> more found explaining using 2.6.0 may trigger some bugs.
> 
> Should you not consider to increase --enable-kernel, at least to 2.6.9?
> 
> Gilles
> 
 Thanks for the reminder.  The last time this came up (Alexander
reported artsd spamming the log), there was no consensus and it was
clear that I didn't really understand it (and I also didn't see the
messages in my own log).  I was hoping to take a look at it in
detail, but that didn't happen.

 To me, 2.6.9 is ancient history! (4 years old).  I think something
like 2.6.16 (purely because it is still getting long-term support
updates) is a better minimum, but also I think we should encourage
people to build a new kernel first (if they aren't using a Live CD)
so that they can be sure it works with their .config, and then they
can use --enable-kernel=current.

 Certainly, my own builds now use --enable-kernel=current (i.e.
running kernel and the headers I build are the same).

 My impression is that setting it later than the running kernel will
worst-case cause the build to fail when the glibc in chroot tries to
use an interface that isn't available.  But, I don't encourage
people to build new systems while running an old kernel!

 To save people googling for the original thread, the new things are
listed in sysdeps/unix/sysv/linux/kernel-features.h.

 That 'MIN_KERNEL_SUPPORTED' seems to be a debian thing ?  All the
references on google except for one are to debian lists and bugs.
The other was for glibc-2.2.4 and the symbol was in
debian/sysdeps/linux.mk.  I can't find it in (clfs's) glibc-2.8.

ĸen
-- 
das eine Mal als Tragödie, das andere Mal als Farce



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