* bug#41575: [bug#43371] [PATCH] doc: prevent host/container nscd mismatch
[not found] ` <87y2ld9ym2.fsf@gnu.org>
@ 2020-09-14 1:05 ` conjaroy
2020-09-14 7:26 ` Ludovic Courtès
[not found] ` <87tuw0ddn3.fsf@rdklein.fr>
1 sibling, 1 reply; 3+ messages in thread
From: conjaroy @ 2020-09-14 1:05 UTC (permalink / raw)
To: Ludovic Courtès; +Cc: 43371, edk, 41575
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Hello Ludo',
A separate nscd per container also seems like a reasonable option. However,
for the sake of machines hosting many long-lived containers, perhaps we
should consider reducing the cache size: currently it's 32MB for each name
service type, with an expiration of 12-24 hours:
https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/services/base.scm?id=1042d269a723360a02b19a2baafef1e24a3bfc73#n1115
Cheers,
Jason
On Sun, Sep 13, 2020 at 5:05 PM Ludovic Courtès <ludo@gnu.org> wrote:
> Hi,
>
> edk@beaver-labs.com skribis:
>
> > doc/guix.texi: (Name Service Switch) add a workaround for bug #41575
> > ---
> > doc/guix.texi | 16 +++++++++++++++-
> > 1 file changed, 15 insertions(+), 1 deletion(-)
> >
> > diff --git a/doc/guix.texi b/doc/guix.texi
> > index a6e14ea177..a9472e680e 100644
> > --- a/doc/guix.texi
> > +++ b/doc/guix.texi
> > @@ -1706,6 +1706,20 @@ this binary incompatibility problem because those
> @code{libnss_*.so}
> > files are loaded in the @command{nscd} process, not in applications
> > themselves.
> >
> > +For applications running in containers (@pxref{Invokin guix container}),
> > +however, @code{nscd} may leak information from the host to the
> container.
> > +If there is a configuration mismatch between the two ---e.g., the host
> > +has no @code{sshd} user while the container needs one--- then it may be
>
> I find the example is hard to understand. How about: “applications in
> the container could end up looking users in the host”?
>
> > +worthwhile to limit which kind of information the host's @code{nscd}
> > +daemon may give to the container by adding the following to
> > +@code{/etc/nscd.conf}.
> > +
> > +@example
> > + enable-cache passwd no
> > + enable-cache group no
> > + enable-cache netgroup no
> > +@end example
>
> Actually, perhaps the better fix is to never use the host’s nscd? We
> could change ‘containerized-operating-system’ accordingly.
>
> That would allow guest OSes to work correctly regardless of the host’s
> nscd config, which seems like an improvement.
>
> Thoughts?
>
> Ludo’.
>
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^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#41575: [bug#43371] [PATCH] doc: prevent host/container nscd mismatch
2020-09-14 1:05 ` bug#41575: [bug#43371] [PATCH] doc: prevent host/container nscd mismatch conjaroy
@ 2020-09-14 7:26 ` Ludovic Courtès
0 siblings, 0 replies; 3+ messages in thread
From: Ludovic Courtès @ 2020-09-14 7:26 UTC (permalink / raw)
To: conjaroy; +Cc: 43371, edk, 41575
Hi,
conjaroy <conjaroy@gmail.com> skribis:
> A separate nscd per container also seems like a reasonable option. However,
> for the sake of machines hosting many long-lived containers, perhaps we
> should consider reducing the cache size: currently it's 32MB for each name
> service type, with an expiration of 12-24 hours:
>
> https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/services/base.scm?id=1042d269a723360a02b19a2baafef1e24a3bfc73#n1115
Good point.
In that case, we can have ‘containerized-operating-system’ provide its
own NSS configuration with a reduced cache size (or without cache since
there’s caching happening on the host for host name lookups, for
instance).
WDYT? Would you like to give it a try?
Thanks,
Ludo’.
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#41575: [bug#43371] [PATCH] doc: prevent host/container nscd mismatch
[not found] ` <87tuw0ddn3.fsf@rdklein.fr>
@ 2020-10-05 8:36 ` Ludovic Courtès
0 siblings, 0 replies; 3+ messages in thread
From: Ludovic Courtès @ 2020-10-05 8:36 UTC (permalink / raw)
To: Edouard Klein; +Cc: 41575, 43371-done, conjaroy
Hi,
Edouard Klein <edou@rdklein.fr> skribis:
>> Actually, perhaps the better fix is to never use the host’s nscd? We
>> could change ‘containerized-operating-system’ accordingly.
>>
>
> I think this would be best, but I did not know where to make this
> change, so I just edited the doc instead. I don't know if containers
> need the host's nscd to avoid the libc issues mentionned in the doc, but
> if they dont, then prevening them from accessing the host's nscd seems
> logical and would solve the problem. And we wouldn't need to amend the
> doc at all.
This has now been done by Jason in
5627bfe45ce46f498979b4ad2deab1fdfed22b6c.
Closing!
Ludo’.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-09-14 1:05 ` bug#41575: [bug#43371] [PATCH] doc: prevent host/container nscd mismatch conjaroy
2020-09-14 7:26 ` Ludovic Courtès
[not found] ` <87tuw0ddn3.fsf@rdklein.fr>
2020-10-05 8:36 ` Ludovic Courtès
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