Oh, I know the answer to that one!  

if you're also binding in Samba to winbindd or equivalent, then when sssd renews the machine account passwords monthly it also has to inform samba of that new machine account password.  So that it can stash it away in its secrets store.  

I believe that Samba even provides some helper script or program that you can call -- passing in the new monthly password.  So adcli update could call such a Samba heiper script.


On Fri, Oct 8, 2021 at 8:58 AM Patrick Goetz <> wrote:

On 10/7/21 12:01, Spike White wrote:
> FYI -- update on this situation.
> AD DC logs no help.  They show the exact same response sent back to a
> good machine account password renewal as for a failed renewal.
> One of the AD administrators have identified a particular AD DC NIC
> teaming configuration that they state has caused problems with Kerberos
> on the past.  It's on a small percentage of their AD DCs and they will
> work to correct.  They will keep us apprised as to update.
> I'm skeptical that's the underlying root cause -- for two reasons:
> 1.  If Kerberos was sensitive to this, it should affect all Kerberos
> operations  (Kerberos auth, etc.) and not just the kpasswd operations.
> 2. This is not occurring on our older RHEL6 and RHEL7 builds AD
> integrated via our older commercial AD integration product.  It's
> occurring only on our sssd-integrated builds.
> At this point, we're turned off debug level 7 (it was filling up our
> /var/log filesystems and we have the verbose adcli update output from at
> least two failed clients).   We're going to take the alternate
> suggestion of setting ad_maximum_machine_account_password_age to 0
> (disabling sssd from updating password) and run a cron job to do 'adcli
> update'.
> We're wrapping this adcli_update with tcpdump to get the exact kpasswd
> request/response packets, as well as wrapping with KRB5_TRACE.
> We want to call adcli update exactly as sssd calls it. 
> From SOURCES/sssd-2.4.0/src/providers/ad/ad_machine_pw_renewal.c, this
> appears to be how sssd calls external program /usr/sbin/adcli to do its
> adcli update:
>        /usr/sbin/adcli update --verbose --domain=$AD_DOMAIN
> --host-keytab=/etc/krb5.keytab --host-fqdn=$FQDN
> --computer-password-lifetime=30
> because we aren't doing any Samba stuff.

Question: how would Samba stuff be relevant to updating the Kerberos
ticket using adcli?

   Is that the correct
> invocation?   We'll set computer-password-lifetime lower, say to 7. 
> Because we want to see examples more frequently, to find failed updates.
> BTW, the packet capture on a successful machine account password renewal
> is only 8K, so that very targeted debug will not swamp our /var/log or
> /tmp filesystems.
> Spike
> On Wed, Aug 25, 2021 at 10:32 AM Spike White <
> <>> wrote:
>     Sssd experts,
>     *_Short summary:_//* How can we troubleshoot sssd’s ‘Automatic
>     Kerberos Host Keytab Renewal’ process?    We have ~0.4% of our Linux
>     servers dropping off the AD domain monthly.
>     *_Longer explanation:_*
>     Over the past two years, we have on-boarded sssd as our Linux AD
>     integration component.  Largely displacing a former commercial
>     product that did the same.
>     We have about ~20K Linux servers that are sssd-enabled.  A mix of
>     RHEL6, RHEL7, RHEL8, Oracle Linux 6, 7 and 8.   We have ~7K Linux
>     servers still on the old commercial product.  (For certain edge-case
>     scenarios, such as DMZs, the commercial product works better.)
>     Our AD forest is a single AD forest, with 4 regional child domains.
>     All with transitive trust.  Sssd auto-discovers parent domain and
>     all 4 child domains, no problem – whenever it’s adcli joined to its
>     regional local domain.
>     Why are I writing this?
>     Because we are researching an ongoing problem reported by L1 server
>     ops.  About 70 – 80 sssd-enabled Linux servers / month drop off the
>     domain.  Out of our current sssd-enabled population of ~20K server,
>     that’s not horrible.  But still it should be better.  (Our former
>     commercial product did better.)
>     It’s not limited to one particular OS, OS version, build location or
>     region.  We have surveyed; it seems to occur randomly among all OS
>     versions, regions and locations.
>     To be clear, it’s extremely likely that this behavior arising from
>     some subtle misconfiguration on our part – not from any sssd or
>     adcli or Kerberos bug.  We have a couple of configuration
>     improvements we’re pursuing. (Kerberos max ticket lifetime mismatch
>     between AD and /etc/krb5.conf file for instance.)
>     We are taking sssd’s default settings for
>     ad_maximum_machine_account_password_age and
>     ad_machine_account_password_renewal_opts. So after 30 days, sssd
>     will attempt daily to renew the host Kerberos keytab file.  It
>     should re-attempt daily if not renewed.  By company policy, our AD
>     disables any machine accounts that have not renewed their
>     credentials in 40 days.   So when we find servers that have dropped
>     off the domain, it’s because they have not renewed their AD machine
>     accounts in 40 days.
>     We have SR’s open with our OS vendors (Redhat and Oracle
>     respectively) for months now.  To no great help.  (They gave a few
>     suggestions, but none panned out.)
>     We thought we were hitting this bug:
>     <>
>     But packet captures proved that adcli update is using TCP on
>     RHEL7/8.  Thus, this might be a potential problem, but only on
>     RHEL6.  (BTW ‘udp_preference_limit = 0’ doesn’t force use of TCP for
>     the kpasswd invocation in RHEL6 – it still uses UDP.  Thus, the
>     recommended work-around for this bug doesn’t work.)
>     So that isn’t our underlying problem.
>     We’re at a loss now – as you can see, we’re grasping at straws.
>     How can we troubleshoot sssd’s ‘automatic Kerberos Host keytab
>     renewal’ process?  Whenever we inspect a particular server it
>     works.  We can’t run all sssd clients at debug level 9;  it fills up
>     /var/log filesystem after a few days of that.  We’re interested in
>     troubleshooting that one particular sssd process on all clients; not
>     all parts of sssd.
>     Other than a steep learning curve (on our part), obscure situations
>     (like DMZ auto-discovery of AD controllers) and exotic scenarios
>     (like above), we’re quite happy with our 2 yr journey of direct AD
>     integration with sssd.    Obviously, the troubleshooting tools on
>     RHEL6 are very minimal.  But certainly, overall the quality of sssd
>     on RHEL7/8 is excellent. AD integration has innumerable devils in
>     the details; I’m amazed that sssd performs as well as it does
>     against our multi-domain forest.
>     Spike
>     PS the problem with sssd auto-discovery of AD controllers in DMZs
>     has been fixed in a recent sssd release. The better discovery
>     algorithm was implemented – same one used by Windows clients and
>     commercial products. It’s just that recent sssd version is not on
>     RHEL7 or 8.
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