Nicholas Hinds via FreeIPA-users wrote:
During an upgrade from 4.5.0-21.el7.centos.1.2 to 4.5.0-21.el7.centos.2.2 on a CentOS 7.4 machine, FreeIPA's DNS server briefly returned NXDOMAIN for records which existed in FreeIPA. These invalid responses were returned for a very short amount of time, but caused long-running issues with Java clients which tend to cache DNS responses. Upgraded packages included: 389-ds-base, 389-ds-base-libs, 389-ds-base-snmp, ipa-client, ipa-client-common, ipa-python-compat, ipa-server, ipa-server-common, ipa-server-dns, ipa-server-trust-ad, python2-ipa-server, and a dozen sss-related packages.
I reproduced this in a FreeIPA test environment by running `while true; do dig some.dns.entry.managed.by.freeipa @ip.address.of.freeipa | tee -a a-log-file; done` from one server, and running `yum update` on the FreeIPA machine. The invalid NXDOMAIN responses were returned some time after the `yum update` logged 'Cleanup' for the RPMs, and seemed to be during the 'Verifying' phase.
These NXDOMAIN responses claimed that an upstream nameserver (a.root-servers.net http://a.root-servers.net) was the authority for my zone:
a-log-file-; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6_7.7 <<>> some.dns.entry.managed.by.freeipa @172.16.0.77 http://172.16.0.77 a-log-file-;; global options: +cmd a-log-file-;; Got answer: a-log-file:;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 2889 a-log-file-;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0 a-log-file- a-log-file-;; QUESTION SECTION: a-log-file-;some.dns.entry.managed.by.freeipa. IN A a-log-file- a-log-file-;; AUTHORITY SECTION: a-log-file-.60INSOAa.root-servers.net http://a.root-servers.net. nstld.verisign-grs.com http://nstld.verisign-grs.com. 2017102400 1800 900 604800 86400 a-log-file- a-log-file-;; Query time: 227 msec a-log-file-;; SERVER: 172.16.0.77#53(172.16.0.77) a-log-file-;; WHEN: Tue Oct 24 18:30:28 2017 a-log-file-;; MSG SIZE rcvd: 130
Usually when querying an invalid DNS entry, the dig output still claims that my FreeIPA server is authoritative for the zone: $ dig doesntexist.zone.managed.by.freeipa @172.16.0.77 http://172.16.0.77
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6_7.7 <<>> doesntexist.zone.managed.by.freeipa @172.16.0.77 http://172.16.0.77 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 59953 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION: ;doesntexist.zone.managed.by.freeipa. IN A
;; AUTHORITY SECTION: zone.managed.by.freeipa.30 INSOAidm01.freeipa. hostmaster.zone.managed.by.freeipa. 1508869828 30 900 1209600 30
;; Query time: 0 msec ;; SERVER: 172.16.0.77#53(172.16.0.77) ;; WHEN: Tue Oct 24 19:27:12 2017 ;; MSG SIZE rcvd: 113
Is it possible that during a yum update, the FreeIPA DNS server temporarily forgets what zones it's authoritative for (or forgets all DNS records) and just delegates to the upstream DNS server for half a second or so? Or is something else going on here?
I'm open to suggestions.
The LDAP server is brought down during upgrades which is likely the issue. bind can't connect to its backend. Why it returns NXDOMAIN I don't know.
You may be able to manually work around this by manually stopping bind before updating IPA, then starting it again afterwards.
rob