[Samba] Issue with pam_winbind for MS AD authentication and moduleoptions

Andre Fernando Goldacker samba at teka.com.br
Wed Apr 4 14:57:55 GMT 2007


passwd, shadow and group looks as follows in nsswitch.conf:

passwd:  files winbind
shadow:  files
group:     files group

What really confuses me is that when my AD server is up and running,
root or any local user logs in with no problem.
And even when AD server is down, after trying a zillion times, root and
other local users login, and then if I log them out and try again a few
minutes later it won't go again, then again after a few minutes it works
again and it keeps going like that.

My guess is that when it's not going pam_winbind and winbind are trying
to connect to the AD Server resulting in a huge delay in the login
process afecting also local users login. That's why I was wondering if
there is a "timeout" option or something for pam_winbind to avoid that.
Well, that's my guess I could be wrong and maybe the problem is
something else.

Anyway thank's so far for your help, if you or anyone has a light...


Miles, Noal wrote:
> You have files before winbind in /etc/nsswitch.conf for passwd, shadow,
> group?
> Noal
> -----Original Message-----
> From: samba-bounces+noal.miles=tdstelecom.com at lists.samba.org
> [mailto:samba-bounces+noal.miles=tdstelecom.com at lists.samba.org] On
> Behalf Of Andre Fernando Goldacker
> Sent: Wednesday, April 04, 2007 8:40 AM
> To: samba at lists.samba.org
> Subject: [Samba] Issue with pam_winbind for MS AD authentication and
> moduleoptions
> Hello!
> I've configured samba with winbind and pam_winbind module to
> authenticate users that connect to my linux box against MS AD.
> Works like a charm. If a user exists both in AD and locally, login
> should assume local users. Again, it works pretty well (It seems at
> least with my current config).
> If my AD server goes down for any reason, local users should be able to
> login. For example, root has to login always no matter if my AD server
> exploded.
> That's where is the problem. When I shutdown my AD server and I try to
> login with a local user (root as well), my guess is that it seems that
> pam_winbind waits for a very very long time trying to find my AD server
> to authenticate that even the local login times out. I don't really know
> if that is the reason for this behaviour, but if it is, I'm wondering if
> there is a hidden or maybe a new "timeout" option for pam_winbind module
> as I didn't found anything related in the man pages and the mailing
> lists archive. Or maybe if login finds the user in the local database,
> bypass winbind authentication, don't know if that is possible.
> The reason why I came up with this idea is that when the AD server is
> down and I try to login with root for eg. over and over many times,
> after a while it goes (looks like pam config order is right), but a few
> minutes later it won't again, which made me thought that perhaps winbind
> or pam_winbind are trying to estabilish a connection with AD and somehow
> because of that the whole process slows down so much that even local
> login times out.
> Samba is configured to catch UID's, GID's from AD using SFU and ad idmap
> backend. Only users that are members of a specified AD group are able to
> login. The purpose of the machine is to be an application server and
> share folders based on AD users and group permissions.
> My system is RHEL AS3 with update 7 and samba-3.0.24
> Below are my pam lines in the system-auth file:
> #%PAM-1.0
> # This file is auto-generated.
> # User changes will be destroyed the next time authconfig is run.
> auth        required      /lib/security/$ISA/pam_env.so
> auth        sufficient    /lib/security/$ISA/pam_unix.so likeauth nullok
> auth        sufficient    /lib/security/$ISA/pam_winbind.so
> try_first_pass require_membership_of=DOMAIN+group
> auth        required      /lib/security/$ISA/pam_deny.so
> account     required      /lib/security/$ISA/pam_unix.so nullok_secure
> account     sufficient    /lib/security/$ISA/pam_winbind.so
> password    required      /lib/security/$ISA/pam_cracklib.so retry=3
> password    sufficient    /lib/security/$ISA/pam_unix.so nullok
> use_authtok md5 shadow
> password    required      /lib/security/$ISA/pam_deny.so
> session     required      /lib/security/$ISA/pam_limits.so
> session     required      /lib/security/$ISA/pam_unix.so
> session     required      /lib/security/$ISA/pam_mkhomedir.so umask=0022
> skel=/etc/skel
> Considering that if a user exists both in the local user database and
> AD, login has to assume local user (seems to be working fine), could
> someone give me a hint if I'm in the right path, and maybe an idea why
> or what I could do when my AD servers goes down to my local users
> (including root) log in normally??
> Any help will be greatly appreciated,
> Andre

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