I have an older CentOS 6 / ISPConfig 3.2.5 machine (3.2.6 breaks it, so we don't go there). i'm in the process of phasing it out, but there is some custom stuff on there that I just can't move yet. That said, it periodically loses it's DNS entries in /etc/resolv.conf. I only know it because it'll complain that it can't resolve a known (but not local) domain, and I'll check, and it'll be empty. This time, I opened up the ISPConfig -> System Tools -> System Config and removed and reentered the desired IPs, and saved them, and when it was done updating the config, i checked resolv.conf, and they still were not there. And it could not resolve the domain. I added them manually to resolv.conf, restarted named and it started resolving again. So i'm wondering if IPSConfig is storing that nameserver info somewhere else, not at all, or if it's supposed to store them in /etc/resolv.conf, and if so, what might be causing it to not put them there. is there some other configuration update that might overwrite the /etc/resolv.conf file periodically, and not be putting the DNS entries back in there like it should be? or does it not even put them there to begin with? I did check my other CentOS 8 / ISPConfig 3.2.7 and the resolv.conf file there looks like it was Generated by NetworkManager, so I'm guessing that's from when the system was installed initially, and has not been updated by ISPConfig since, even though those IPs are in the System Config. That would imply that setting the nameserver settings in Server Configg doesn't mean that it's actually going to set those values anywhere currently, corrrect? Nothing critical currently, just curious at this point. Thanks.
ISPConfig is not periodically checking or updating resolv.conf file. Is this a virtual machine? If yes, then the resolv.conf file might be updated by the virtualization system. There might be other services as well, e.g. DHCP, that can change network settings.
Thanks. not a virtual machine. no dhcp either. curious why the System Config asks for DNS servers if it doesn't put them to use. Seems like it really should be an essential configuration setting.
They must be set correctly before you even start installing ISPConfig on the server as apt/yum won't be able to download any packages without functioning DNS resolution and it is very unlikely that one would ever have to change them afterward. As I mentioned earlier, your issue of changing resolv.conf file is not ISPConfig related.
