Problem: A new server cannot be installed due to DNS error

[scheinig]

Problem:

A new server cannot join because of DNS error

“Unter der Adresse des DNS-Servers konnte kein Domänencontroller gefunden werden. Die Netzwerkeinstellungen sollten überprüft werden.”

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“No domain controller was found at the address of the name server. Please adjust your network settings.”

Solution:

You can try the following steps to find the root cause and/or solve the issue:

Step1:

Check firewall and ports.

Which TCP / UDP ports on the DC master must be accessable by other UCS systems?

Systems in a UCS domain must be able to establish TCP/UDP connections to the DC master for several services. If a firewall or other port-blocking devices are used in a site-configuration, this functionallity may be disturbed and ports must be opened directly. The following ports are essential: Port Protocol Service 22 TCP SSH 53 TCP/UDP Nameserver 88 TCP/UDP Kerberos 123 TCP/UDP NTP 443 TCP HTTPS 464 TCP/UDP Kerberos 749 TCP/UDP Kerberos 6669 TCP Univention Directory Notifier …

Step 2:

Check the DNS settings on the slave. The master has to be set as DNS server.

Step 3:

Check if the master has more than one interface, make sure they are all propery configured.
Withdns/backend=samba4 check if these interfaces are properly used by samba

ucr get samba/interfaces
ucr get samba/interfaces/bindonly

Step 4:

Simply try to restart the bind9 service on the master:
systemctl restart bind9.service nscd.service

Step 5:

Check the following service Record to be resolvable

On the master:

dig _ldap._tcp.schein.me SRV

;; ANSWER SECTION:
_ldap._tcp.schein.me.   10800   IN      SRV     0 100 389 master.schein.me.

;; AUTHORITY SECTION:
schein.me.              10800   IN      NS      master.schein.me.

;; ADDITIONAL SECTION:
master.schein.me.       80600   IN      A       10.200.43.30

On the Slave you want to join, if you are in a virtual environment and you can switch to a built-in shell

# chroot /target
# bash
dig _ldap._tcp.schein.me SRV