[Samba] Domain member cannot authenticate when first domain controller is down

[Dale]

Unfortunately, after making the resolv.conf and krb5.conf changes, 
things actually became worse.  All connection attempts timed out, even 
after reverting krb5.conf back to the way it was.  For completeness, I 
disabled pam_winbind.conf to make sure that a cached login was not 
interfering.

The strange thing is that I can see all sorts of successful SRV query 
results in the BIND query logs of DC2.  The "options rotate"in 
resolv.conf has had a significant effect.  Counting the SRV queries in 
old BIND log files (query.log.x) shows only a handful of SRV queries per 
log file.  Since adding the rotate option, SRV queries are in the 1000's 
per log file.  So, it's doing something, but not failover in any form or 
fashion.

@Jason

I now have a bugzilla account and will add the "me too".

Dale


On 3/3/21 5:16 PM, Josh T via samba wrote:
> I saw a reasonable improvement from including this line at the top of resolv.conf:
> options rotate timeout:1
>
> I can now consistently log in to domain members. There is still a ~20 second delay, but I can live with this. Are there any downsides to setting the timeout so low? I haven't experimented with other timeouts yet.
>
> As per Louis's suggestion, I ran "dig ns $(hostname -d)", and it does show all AD-DC servers. I also verified that the directory "/var/cache/samba" exists. I can see that the smb.conf option "cache directory" is already set to this value using "testparm -v".
>
> Regards,
>
> Josh
>
>
> ________________________________
> From: Dale <samba at txschroeder.family>
> Sent: Wednesday, March 3, 2021 12:08 PM
> To: samba at lists.samba.org <samba at lists.samba.org>; Jason Keltz <jas at eecs.yorku.ca>; Josh T <c3h4ohcooh3 at hotmail.com>; Kris Lou <klou at themusiclink.net>
> Subject: Re: [Samba] Domain member cannot authenticate when first domain controller is down
>
> On 3/3/21 9:58 AM, L.P.H. van Belle via samba wrote:
>
> Check the following.
>
> dig ns $(hostname -d)
> You should see all the AD-DC servers, if not add the NS record of the missing ones, then when thats done.
>
> try these settings and test what works best for you, add in /etc/resolv.conf
>
> options timeout:3
> options attempts:2
> options rotate
>
> (see : man resolv.conf what these do)
>
> in smb.conf..
> Try setting :
>
> cache directory = /var/cache/samba
> (do check if the folder exists. )
>
> these parts would be the first one's i would look into.
>
> I hope this can help you.
>
> Greetz,
>
> Louis
>
> @ Louis
>
> The dig command returns the correct results, and the cache directory setting already matches what you had suggested.
>
> I will experiment with the resolv.conf options that you mentioned.
>
> @ Jason
>
> I have requested a bugzilla account in order to add a "me too" to your bug report.  If what I'm experiencing is not identical, it is most certainly similar.
>
> @ Kris
>
> I'll need some direction for this -
>
>
> <KL> "Also, are the _kerberos SRV records correct for DC2?"
>
> Where/How do I find this, and what are the expected values?
>
> Thanks to all for the suggestions.
>
> Dale
>
>
>
>
>
> -----Oorspronkelijk bericht-----
> Van: samba [mailto:samba-bounces at lists.samba.org] Namens Dale via samba
> Verzonden: woensdag 3 maart 2021 16:25
> Aan: Josh T; Roy Eastwood; samba at lists.samba.org<mailto:samba at lists.samba.org>
> Onderwerp: Re: [Samba] Domain member cannot authenticate when first domain
> controller is down
>
> Josh, I don't have the answer to your question, but if you ever figure
> it out, I would like to know the answer, too.
>
> The 2nd DC that I built has been of very little use.  While building, it
> passed all the tests in the wiki.  After building, I found some DNS
> entries that were not created during the join. Rowland kindly helped me
> add and/or edit the affected entries, and I hoped for better results.
> However, it was not to be.  If the 1st DC is removed from the network,
> any kind of login or getent is interminably long or times out.  So,
> while I easily see the theoretical value of having multiple DC's, I'm
> having trouble seeing the actual, practical benefit of having them.
> There is no instant failover, and often times, there is complete failure
> of necessary AD functions.  While it's certainly possible the problem
> could be me, I cannot troubleshoot what the problem is.
>
> Dale
>
>
> On 3/1/21 6:25 PM, Josh T via samba wrote:
>
>
> Further fiddling with this has shown something strange. If I enter my
>
>
> username and password in an attempt to authenticate a domain user, it will
> take 60+ seconds for it to fail to log in. However, during said 60+
> seconds, if I log in via SSH as a non-domain user, then the domain user
> login succeeds. What could cause that?
>
>
> ________________________________
> From: Roy Eastwood <spindles7 at gmail.com><mailto:spindles7 at gmail.com>
> Sent: Saturday, February 27, 2021 1:27 AM
> To: 'Josh T' <c3h4ohcooh3 at hotmail.com><mailto:c3h4ohcooh3 at hotmail.com>; samba at lists.samba.org<mailto:samba at lists.samba.org>
>
>
> <samba at lists.samba.org><mailto:samba at lists.samba.org>
>
>
> Subject: Re: [Samba] Domain member cannot authenticate when first domain
>
>
> controller is down
>
>
>
> On 27 February 2021 03:35 Josh T wrote:
>
>
> //Problem:
> I am unable to authenticate a domain user on a Samba domain member
>
>
> while the
>
>
> first Samba directory controller DC1 is powered off and the second
>
>
> Samba
>
>
> directory controller DC2 is powered on.
>
> While DC1 is powered on, I can log in as a domain user with no
>
>
> problems. While
>
>
> DC1 is powered off, attempting to log in usually results in waiting 60+
>
>
> seconds
>
>
> followed by a login failure message. If I had already logged in prior
>
>
> to
>
>
> powering
>
>
> off DC1, then I can see the same long delay and authentication failures
>
>
> when
>
>
> entering my sudo password. Intermittently I can sometimes manage to log
>
>
> in
>
>
> while DC1 is powered off, but there is still the 60+ second delay; I
>
>
> haven't
>
>
> been
>
>
> able to link this intermittent behavior to any of my own
>
>
> troubleshooting
>
>
> actions.
>
>
> In any case, a 60+ second delay is undesirable.
>
> //Environment description:
> The first Samba domain controller DC1 was created following these
>
>
> instructions
>
>
> on the Samba wiki:
>
>
>
> https://wiki.samba.org/index.php/Setting_up_Samba_as_an_Active_Directory_
>
>
> Domain_Controller
> It was provisioned using the command "samba-tool domain provision --
>
>
> use-
>
>
> rfc2307 --interactive".
> The BIND9_DLZ DNS backend was selected during provisioning.
> Samba version 4.11.6-Ubuntu was installed on DC1 using the apt command.
>
> The second Samba domain controller DC2 was created following these
> instructions on the Samba wiki:
>
>
>
> https://wiki.samba.org/index.php/Joining_a_Samba_DC_to_an_Existing_Active
>
>
> _Directory
> It was joined using the command "samba-tool domain join my.domain.tld -
>
>
> -dns-
>
>
> backend=BIND9_DLZ --option='idmap_ldb:use rfc2307 = yes'".
>
>
> The above is missing the letters  "DC" in the command line.   This may
>
>
> be the
>
>
> issue.
>
> HTH
>
> Roy
>
>
>
>
>
>
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