[Samba] winbind causing huge timeouts/delays since 4.8

Remy Zandwijk remy+samba at luckyhands.nl
Sat Feb 23 14:33:17 UTC 2019

> On 23 Feb 2019, at 14:52, Rowland Penny via samba <samba at lists.samba.org> wrote:
> On Sat, 23 Feb 2019 14:21:57 +0100
> Remy Zandwijk via samba <samba at lists.samba.org> wrote:
>>> On 23 Feb 2019, at 14:07, Rowland Penny via samba
>>> <samba at lists.samba.org> wrote:
>>> On Sat, 23 Feb 2019 13:47:54 +0100
>>> Remy Zandwijk via samba <samba at lists.samba.org> wrote:
>>>>> On 23 Feb 2019, at 09:33, Rowland Penny via samba
>>>>> <samba at lists.samba.org> wrote:
>>>>> If you have, as you have, 'files sss winbind' in the the passwd &
>>>>> group line in nsswitch.conf, means this:
>>>>> First /etc/passwd or /etc/group is searched and if the user or
>>>>> group is found, this info is returned.
>>>>> Next sssd will be asked, 'do you know this user or group ?' if
>>>>> found, the info is returned.
>>>>> Finally winbind will be asked, 'do you know this user or group ?'
>>>>> if found, the info is returned.
>>>>> Lets take a user called 'fred', this user is in AD. The first
>>>>> search will return nothing, so sssd is asked, this 'asks' AD and
>>>>> returns the users info. Finally, wait that's it, we have the
>>>>> info, there is no need to ask winbind for anything.
>>>> That is incorrect. Alexander stated:
>>>>> No. we use max. 3 auth providers: (1. and 2. on all unix servers)
>>>>> 1. unix (local passwd)
>>>>> for static OS/service accounts across all our env
>>>>> 2. sssd (with unix ldap servers as provider)
>>>>> unix experienced user and application related service accounts
>>>>> 3. samba/winbind
>>>>> for windows users/services needing access to a group of unix
>>>>> servers
>>>> And:
>>>>> They don't - as stated above we use sssd for query/caching entries
>>>>> from our ldap directory server and not Windows DomainConmtrollers
>>>>> - also this is possible, but makes more trouble and don't provide
>>>>> what samba's smb/windbind does.
>>>> He clearly writes (in multiple emails) that sssd is configured to
>>>> use his unix ldap servers and not AD.
>>>> Maybe three sources of user databases is not regular, but I fail to
>>>> see why this should be a problem (provided that usernames,
>>>> uidNumbers and such are unique across the databases).
>>> And there is the problem, if 'fred' is in /etc/passwd, that user
>>> will be used, but what if you meant fred in ldap or AD ?
>>> There is absolutely no point in having 4 databases (yes there are 4,
>>> Unix, sssd, winbind and the ldap lines in smb.conf), they could all
>>> be combined in AD. 
>>> The main problem is that the OP wants Samba changing to cope with
>>> his mess, it might be a valid change, but the reason for the change
>>> is invalid.
>> Well, I think the problem is you _assume_ users are in multiple
>> databases and we just don't know that. I think there is a good change
>> Alexander perfectly knows what he is doing and users are unique
>> across databases.
>> Nevertheless, at some point nss is clearly querying winbind, which
>> means nss did not find the user in either /etc/passwd nor via sssd.
>> In the case that winbind _is_ queried, Alexander is experiencing,
>> like he wrote, 'frequently system hangs/slowness for a couple of
>> seconds' and he observed that winbind is causing this behaviour.
>> So maybe we should set our focus on winbind instead of the multiple
>> database stuff and figure out why it behaves like this since the
>> upgrade from 4.7 to 4.8. I would say we should start with fixing the
>> winbind stuff in smb.conf. Right?
>> -Remy
>> P.S. I am following this thread since I also noticed occasional
>> 'hangs' when the system is querying winbind. This is Samba 4.8.7 on
>> FreeBSD 11.2.
> I am quite prepared to help in getting winbind working correctly, but
> this will require the OP changing their smb.conf considerably and
> removing sssd. We do not support sssd, it is not a Samba product (for
> want of a better name). Samba on a Unix domain member is designed
> around 3 binaries, smbd, nmbd and winbind, the latter can do just about
> anything sssd can do, so why use sssd ? Now you say that I am making
> assumptions, well about this one, probably somewhere in the mix there
> will be Windows domain members and the users in ldap are unlikely to
> be known to them.

I consider sssd as 'just another' user database, like /etc/passwd (which Samba apparently does support) and I personally cannot see any difference there, but I respect your opinion.

Where is it documented winbind should be the only service which should be used with nss? If it is not documented, maybe it should.

The proof of the pudding is of course, Alexander removing sssd from nsswitch.conf and show us the problem still exists, or better yet, disappeared.

> I have seen quite a few Samba setups that are like this one, bending
> Samba to do something it isn't designed to do, you then get complaints
> that it slow, hangs etc. Probably fixing the set up would stop all
> these problems.
> The OP says that it is sssd that is doing the ldap lookups, yet he has
> these in smb.conf:
> ldap connection timeout = 10
> ldap timeout = 30

Yep, these lines should be removed.

> He also has these:
> idmap config * : rangesize = 1000000
> idmap config * : range = 1000000-19999999
> idmap config * : backend = autorid
> The '*' domain is meant for the Well Known SIDs and anything outside
> the Samba domain. I would have expected something like this:
> idmap config * : backend = tdb
> idmap config * : range = 3000-7999
> idmap config OPS : backend = rid
> idmap config OPS : range = 10000-999999

That should also be fixed.

> If he wants to use Samba in a supported way, then I am more than
> willing to help.

Thanks. Now let's hope Alexander is willing to jump some hoops.


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