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Creating and removing dynamic DNS entries

Some operating systems will register their names in DNS as they boot up (Windows is a notable example). There may also be reverse DNS entries (so that a name can be found from an IP address). If their IP addresses changes or they aren't on a domain, this can go wrong leading to missing or stale records.

For SOLUS to work (to update SIMS), both forward and reverse DNS should be present and correct. When creating application layers with Citrix App Layering, temporary VMs are created and are not domain-joined, so may not have their names registered correctly.

Using the dnsentry command

The dnsentry command (if your system is new enough to have it) is a friendly wrapper to the commands listed later in this page. It has two methods of use:

• dnsentry <name> <IP address> = set up single forward and reverse records for the name and address gives, removing any previous records
• dnsentry -d <name> <IP address> = removes any records for the name and IP address given

To resolve this, get the machine name with the hostname command in Windows and check its IP address. In the example here, it is CITRXAL178014 and the machine has IP address 10.4.11.11. Example usage:

netmanager 1# dnsentry citrxal17801a 10.4.11.119
Deleting...
Adding...
Forward: citrxal17801a
citrxal17801a.school.internal has address 10.4.11.119
Reverse: 10.4.11.119
119.11.4.10.IN-ADDR.ARPA domain name pointer citrxal17801a.school.internal.

Example deletion:

dnsentry -d citrixal17801a 10.4.11.119
Deleting...
Forward: citrixal17801a
Host citrixal17801a not found: 3(NXDOMAIN)
Reverse: 10.4.11.119
Host 119.11.4.10.in-addr.arpa. not found: 3(NXDOMAIN)

Removing dynamic DNS entries

Use delete command in nsupdate. If you specify an IP address, just that record will be deleted, otherwise all records of the given type will be deleted.

Delete all:

netmanager 1# host laptop1
laptop1.school.internal has address 10.0.117.44
laptop1.school.internal has address 10.36.0.238
netmanager 2# nsupdate
> delete laptop1.school.internal IN A
> send
> quit
netmanager 3# host laptop1
Host laptop1 not found: 3(NXDOMAIN)
netmanager 4#

Delete one IP address:

netmanager 1# host laptop1
laptop1.school.internal has address 10.0.117.44
laptop1.school.internal has address 10.36.0.238
netmanager 2# nsupdate
> delete laptop1.school.internal IN A 10.36.0.238
> send
> quit
netmanager 3# host laptop1
laptop1.school.internal has address 10.0.117.44
netmanager 4#

Manually adding dynamic DNS entries

Adding entries is similar, but you must specify the time-to-live (TTL) value:

netmanager 1# nsupdate
> add testdns.school.internal 3600 IN A 10.0.123.123
> send
> quit
netmanager 2# host testdns
testdns.school.internal has address 10.0.123.123