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Re: [Samba] winbind causing huge timeouts/delays since 4.8




On Sun, 24 Feb 2019 19:25:14 +0100
Ralph Böhme <slow@xxxxxxxxx> wrote:

> 
> Am 24.02.2019 um 18:48 schrieb Rowland Penny via samba
> <samba@xxxxxxxxxxxxxxx>:
> > On Sun, 24 Feb 2019 18:28:43 +0100 Ralph Böhme <slow@xxxxxxxxx>
> > wrote:
> >> Am 24.02.2019 um 16:42 schrieb Rowland Penny via samba
> >> <samba@xxxxxxxxxxxxxxx>:
> >>> On Sun, 24 Feb 2019 15:58:39 +0100 Ralph Böhme <slow@xxxxxxxxx>
> >>> wrote:
> >>>> Another thing that a customer has just been bitten by, was a
> >>>> subtle bug in winbindd's idmap cache that resulted in all
> >>>> xid2sid requests going through the idmap backend, iow winbindd
> >>>> issued LDAP requests. With a few thousand users, things came to
> >>>> a grinding halt.
> >>>> 
> >>>> https://bugzilla.samba.org/show_bug.cgi?id=13802
> >>>> 
> >>>> Patch just landed upstream.
> >>> 
> >>> That is the bug I was referring to and probably (amongst all the
> >>> other cruft) what was causing the OP's problem.
> >> 
> >> Unlikely.
> > 
> > It is was I thought, but as the OP's setup is so convoluted, it is
> > hard to say.
> 
> I don't think it's convoluted, it's certainly beyond the simple
> standard setup we all wish everybody was using, but I don't think it
> is broken as is. I just think an appropriate analysis requires more
> resources then is available on the list.
> 
> >>> However, this has nothing to
> >>> do with using the 'ad' backend with Active Directory. We keep
> >>> dancing around this problem, saying things like 'we need to fix
> >>> this', we have been saying this since Samba 4 was released.
> >> 
> >> Which problem? Fix what? Been saying what?
> > 
> > There have been numerous discussions about the 'ad' backend over the
> > years and they have all gone nowhere. The 'ad' backend still works
> > in the same way as it did when Samba 4 was released and you still
> > have to store the next uidNumber & gidNumber outside AD if you use
> > the Samba tools.
> 
> Looks like you're mixing AD DC use case with member server use case.
> Can we please keep that seperate? Afaict, the one has nothing to do
> with the other.

So a Samba AD DC has nothing to do with a Unix member server, could
have fooled me ;-)

This is the sort of thinking that is holding Samba back. You use any
Windows domain computer and you get the same identity, You cannot do
this on Unix domain computers.
> 
> >>> Windows Uses the SID-RID to identify the user and the domain it
> >>> comes from, surely we can find a way to do this for Samba, we are
> >>> half way there with the 'rid' backend.
> >> 
> >> I'm not really what "there" implies for you, but it seems
> >> idmap_autorid is eventually the backend that takes you "there". :)
> > 
> > No it doesn't, at the moment, the only way to get the same ID on all
> > Unix machines (this includes DC's) is to use the 'ad' backend.
> 
> Sure. But only certain use cases require the same id on all machines,
> many don't. I'm just saying that you should better not use idmap_ad,
> but instead use eg idmap_autorid unless you're setup requires
> idmap_ad.

I am not saying don't use autorid, I am saying that I will not use it,
I just do not see the point to it, the 'ad' and rid' backends work for
most users. Perhaps if there was more documentation, I might change my
mind, but it took me long enough to understand the 'ad' backend, but
once I did, it all clicked in to place. The other problem is that 'ad'
is the only one that allows you to set individual login shells and Unic
home dirs.

Perhaps that is part of the 'problem', there are just too many winbind
backends.

> 
> > You think autorid is the way forward, well sorry, but in my
> > opinion, it isn't.
> 
> Rowland, this is not about *the* way forward, this is about using the
> right backend at the right time.

No Ralph, it is about *the* way forward, Samba needs to get to the
point that it works exactly like Windows (or better), Samba has to
outdo Windows.

Rowland

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