There are many cases to think of when you want to add an host to foreman and not to check if this host is already known in the DNS environment. Currently foreman always checks if a host is known and denies to add or change a hosts if a duplicate is found.
In our specific case the host added is indeed known at our DNS service, which is separately managed. The DNS proxy is not enabled and thus active so this check should not be made. (in this environment Foreman does not manage the DNS and DHCP servers)
Another example could be a different (test)cluster which has it’s own DNS server and dns-proxy but ignores the authoritative DNS servers effectively ignoring DNS entries. So if a host in this cluster resolves any entry the local (foreman managed) DNS server should give different answer from the external authoritative DNS servers. The duplicate checking is done by the Foreman server (and not the proxy, where I think it should be done) and in this case also denies updating.
While this example is more fore test environments we do actually have these kinds of setups.
The proposed change in the support ticket should solve these issues.
Thanks for describing the motivation, I actually miss how to do the change. As we discussed in the thread, creating an option called Check DNS for conflicts would do it. If set to false, Foreman will not do the DNS check.