I am still "confused" about how people are using this VPS for setting up private nameservers/ secondary name servers.
I have a domain.com. I have updated nameservers to ns4 - ns7.urlhasbeenblocked.net.
I need to use ns1.domain.com and ns2.domain.com and give it to my customers. How do i do the same? I have webmin installed on Fedora.
Any help is appreciated.
It sounds like you are confusing running/hosting your own DNS servers and utilizing CVPS's nameserver service.
If you run your own DNS servers, as I do, you need to install a DNS service, most common is Bind9, and configure it to respond to DNS queries. You would then configure the NS record for your domain, with the respective registrar, to point to your VPS server's IP. You can create a host record, ie: ns1.domain.com, to point to one of the IPs, and then setup ns1.domain.com as the primary NS server.
Keep in mind that this is much more complicated then simply using a provider's DNS service. You also should run at least two instances, ideally sync'd with eachother, on two different machines/networks/etc. for redundancy. If your server(s) go offline for any reason, no one will be able to go to any of your domain addresses.
However, you may also chose to use a providers DNS service, Your registrar probably provides this for free, or you could use CVPS's. Odds are, the former option would be superior to the latter in most cases. If you go this route, you would set your domain(s) NS servers to whatever the provider tells you to (ie: ns1.urlhasbeenblocked.com, etc.).
You could also run your own and use a provider for backup (or vice versa), but most providers (AFAIK) don't let you sync yours to theirs, which means any change would need to be done manually on both/all.
Clear things up?