“Shortnames” if you mean only hostnames, is not something that exists in DNS records. That’s a shorthand stemming from automatic dns suffixes on clients, and netbios things that has stuck around forever. A shortname to DNS would actually be like a TLD and might not function the way you expect.
DNS organizes resources records in a tree format, starting with the root zone (.). Next are TLDs (also known as first level domains). Then second level domains (domain.tld.). Yes the dot is technically there in DNS, but it’s omitted in queries for a good reason, explained later. Then you have third level, fourth level, etc until you get to a hostname.
Groups of this DNS tree can be controlled by one DNS server, and this is called a zone. Typical deployments means your DNS server will be in control of one zone, and in that zone, it should have control of the domain level that your hosts are being added to.
When you add records, your DNS software should be presenting the resource record only if you are querying the FQDN, and true “shortname” queries should be returning NXDOMAIN (doesn’t exist). There’s a catch to this though.
In both windows and linux, there is a function called “dns suffix” and “domain search lists”. They perform the same thing. Basically, when you type in a short name, it will append the dns suffix and walk the domain short list until it gets a satisfactory response. This is how you should be configuring your network and clients for using “shortnames”; give them a dns suffix or domain search list if you are using more than one domain, and what they are actually doing is converting it to a proper FQDN before doing the lookup.
Just be advised: if you have dns suffixes and domain search lists defined, this will get in the way of your troubleshooting. There’s an easy way around that though, all DNS clients are supposed to support a way to bypass all of that, by terminating a query with a dot (.). So if you are testing your DNS functionality, hostname.domain.tld. (dot on end included) should query “hostname.domain.tld” and ONLY that. If you need to test and make sure hostname bare doesn’t return anything, you would query for “hostname.” and unless it’s a known TLD, it should return NXDOMAIN.
So to summarize: you should only have DNS returning records for FQDN queries. You can configure clients, such as truenas, with their DNS suffix or add it to the domain search list so that “shortnames” work too. That way when the clients consult DNS and are only given a hostname reference, they will append your domain automatically.
Shortnames, which to DNS are hostnames at the root zone, should not exist in DNS. The root zone is special and should not have entries in it other than TLDs for your use case.
