DHCP fails to assign IPV4 nameservers in /etc/resolv.conf = Cloud-Init + Cpanel + IPV6 Issue? Delayed WHM Login
Answered
I've been using Cpanel for at least 15 years and I've run into this problem in the last month on two new VPS on two different hosting providers. I'm not sure what is different with these host providers or with Cpanel since I haven't seen this happen before.
One host is recommending disabling Cloud-Init. I would prefer to retain DHCP assigned IP and gateway address so the IP addresses of my instances can be changed from the cloud control panel. But if I modify the /etc/resolv.conf file to add Google's IPV4 nameservers it gets overwritten on reboot to only have the two IPV6 nameservers. What's even more strange is on at least one of the hosts, Cpanel eventually reports that the IPV6 nameservers are not working (partial nameserver failure notification.)
This appears to me to be an issue with how Cpanel is handing VPS that have IPV6 addresses assigned. Why it's not assigning the IPV4 IP address and gateway but not the nameservers is just bizarre.
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Hey there! I'm not sure I understand the issue you're running into, but if the resolv.conf entries are being regenerated when the server is rebooting, that's something you'd want to bring up with the hosting provider or datacenter. I'm also not familiar with any DHCP processes related to that particular file.
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I already have and it's quite comical that two different providers acknowledged that, understandably, the linux image uses cloud-init and dhcp by default for maximum. This is both Ramnode and Hetzner. Not obscure hosting providers. Cpanel specifically states the server should have a static network config that doesn't use DHCP.
There's three questions that remain.
1) I've installed probably 20 Cpanel servers in the last 10 years at 4 different hosting providers. Never ran into this issue until now.
2) Why doesn't the Cpanel install just make the changes along with all the gazillion changes it does to the system anyway? I'm sure I'm not the only one running into this.
3) Some hosting providers provide a VM image that includes Cpanel (usually if they are a Cpanel reseller) which probably has the correct static network config. Hetzner isn't a Cpanel reseller so I give them a pass. But Ramnode, being a Cpanel reseller really should offer Cpanel as an option at instance creation which configures the network properly.
At the end of the day it's the sysadmin's responsibility on an unmanaged VPS, I have no problem with that. But as a matter of optimal service setup from a customer service standpoint be it from the hosting provider or Cpanel, I'm a bit disappointed a more proactive strategy isn't being taken on Cpanel instances.
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For question 2, what changes are you expecting us to make? When the server is deployed initially, your host sets the resolvers and cPanel itself never does anything with that file after that point. There should be something in that file that says "generated by dhclient-script" or something similar, but let us know how you think that could be improved and I can talk to the team about it.
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Seems like the installation process should be able to detect O/S setup, and perform these operations automatically?
Static IP Configuration (Cloud) - RamNode
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I spoke with the team and they confirmed that cPanel doesn't have control over those files, and it's not something we want to add to the product. We leave that configuration up to the provider to ensure the network is configured properly before cPanel is installed.
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Really appreciate you taking the time to look into this. This is what I expected. While it would be convenient for Cpanel to modify these files to maintain its requirement of a static network interface configuration, I think the responsibility, from a support perspective, should fall on the hosting provider that is creating the images for instance creation. Cpanel resellers that provide an image that includes Cpanel pre-installed should also dynamically perform these network configurations at the time of VM creation.
Unfortunately only a portion of hosting providers that are Cpanel resellers even give the option of pre-installed Cpanel which then of course leaves it to the SysAdmin to perform the changes. Resellers like Ramnode at least provide the instructions.
Although Cpanel can't modify the files, maybe a prominent warning could be displayed during install: "Warning: DHCP network configuration detected. Cpanel requires static network configurations. Please see these instructions (link to instructions for various operating systems)
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