F18 users unable to log in due to cached nsswitch.conf

Simo Sorce simo at redhat.com
Wed Oct 17 17:02:43 UTC 2012

On Wed, 2012-10-17 at 18:29 +0200, Stef Walter wrote:
> On 10/17/2012 06:21 PM, Miloslav Trma─Ź wrote:
> > That's rather far from actually fixing the problem.  Can we get it
> > fixed_first_?  It seems that we could drop the glibc caching,
> Obviously dropping the caching would be pretty nasty. Having to dlopen 
> the modules each time you do a getpwnam() (or friends) isn't cool.
> I assume you mean fstating the file on each lookup? I'm not against 
> this, and I can try and propose this to glibc, but I'm pretty sure 
> what's going to happen. See similar /etc/resolv.conf discussions.

This would kill perf. which is why it is not done.

> > or by
> > modify authconfig to instruct the user to reboot after changing
> > /etc/nsswitch.conf .
> That's *really* ugly, and prevents tools (like ipa-client-install or 
> realmd) from completing an initialization in one shot. They would have 
> to be split into two parts, with a reboot in between. :S

Yeah, extremely painful and unnecessary, please let's avoid this.

> > I'm not opposed to changing the default nsswitch.conf to avoid that
> > reboot (well, I think it's ugly to refer to a non-installed module,
> > but that's an aesthetic, not a principal thing) and to improve the
> > user experience in the default case, but we do need to have some way
> > to fix the underlying problem, a better way than just giving up and
> > conceding that nsswitch.conf can't be edited from now on.
> We are working on it and I linked to that bug in my report. Ray Strode 
> and I are working on patches to glibc.
> http://sourceware.org/bugzilla/show_bug.cgi?id=12459
> Obviously, if you have another idea of how to fix this other than the 
> above, this would be a great place to put it forward.

Long term I thin I can add support for the nscd protocol to sssd, it
does work around this issue, but has other drawbacks which is why we
haven;t done it so far.

Stef can you open a ticket so we discuss and consider whether to do it ?

This will take time however, in the meanwhile it would be really nice if
we could do it the simple way by just adding sss by default until a
better solution is found.


Simo Sorce * Red Hat, Inc * New York

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