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

Wed Mar 3 23:16:28 UTC 2021

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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