Will the upgrade be a like the current Centos installation, or do I need to reinstall packages, do I nedd to remove packages I dont need.
Basically it is a server running IP-tables started by a script (Arnos IP-TGables firewall script)
DNS-server
DHCP-server
SSH-server
Webmin
That is basically all that is running.
The setup is headles, I am using Webmin and SSH to admin the server.
First of all, Rocky does not support in-place conversion to different major version of EL (e.g. CentOS 7 → Rocky 8, or Rocky 8 → Rocky 9). If you need help with (or info about) ELevate, then ask from its authors (e.g. AlmaLinux OS Foundation Chat ) – and if things do break, then you get to keep the pieces.
Personally, I prefer fresh install and have never used ELevate (although once did almost consider it).
Lets consider what the conversion does. It must first read the list of currently installed packages (A), and current config (B). Then create a new list of packages (C) that are equivalent to A, and new config (D) appropriate for C that is equivalent to B. Finally, install C and remove A, and replace B with D. If parts of A and B are unregognized, then creating C and D for those parts is beyond what the conversion script can do.
So no, the conversion is not likely to install “extra” packages. You might have to uninstall some packages to get the conversion run (to “fix the issues”) and (re)install afterwards.
If you do fresh install, then it is you who has to figure out which packages (of the new distro) you do need and how to translate your config for them. (I condider this a bonus – an incentive to learn the new distro.)
Note on IP-tables. The kernel in Rocky has nf_tables. One can see current ruleset with nft list ruleset. There is still tool iptables but it is a wrapper that translates your IP-tables syntax into nf_tables rules. There is also a script that translates IP-tables syntax rules into nft syntax to ease adoption of nftables.service. The default (to manage firewall) in Rocky is firewalld.service.
If all you need is DNS and DHCP servers (SSH is included even in minimal install), then their config ought to be trivial to copy/adapt to a fresh install. Likewise, “firewall script” probably runs ok but if you can port it to “native nf_tables”, even better. I’ve never used Webmin, nor the “Cockpit” that is in Rocky, but that too sounds “trivial” to install into fresh system.