Updating IP (Range) on Servers in a Small Cluster

[norsemangrey]

Hi guys. I'm in a bit of a squeeze. I have set up three small machines running Proxmox (8.3 / 8.4) in a cluster. Mostly just to be able to move VMs between them if required. The one running 8.3 is out of the picture as the two others has been moved to a new location for a demo. No issue really until I was told we have the wrong IP range for a remote connection. So now I need to change the IP (outside the previous range) on the the two remaining servers in the cluster. I know this is not recommended, but unfortunately I have no other choice.

As I have understood I need to modify the following files, with a new IP, but after that it is a bit unclear:

/etc/network/interfaces
/etc/hosts
/etc/pve/corosync.conf

For one thing I am not able to update the "/etc/pve/corosync.conf" file. It is in read-only. I tried to stop the corosys service and the pve-cluster service, but then the file is gone from that path.

It is also mentioned several places that I only need to update this on one server when changing the server IP (I guess it will be synched), but what about when I need to change the IP on both servers in the cluster? Do I then also modify it on just one of the machines, and will the actual interface IP on both machines (changing
/etc/network/interfaces and /etc/hosts) have to be changed prior to updating this file?

Hope someone can give me a bit of clarity on how to proceed, without messing everything up.

 

[SteveITS]

You can change IPs in the GUI but when you click to Apply will (presumably) lose your connection over the old IP. For a new server we set it up in our lab, when done change the IP, and connect via IPMI/BMC to shut it down to move it into service. I've not changed a live cluster though. Note if the cluster servers don't have a quorum they will restart...

You can edit corosync.conf, are you logged in as root? https://pve.proxmox.com/pve-docs/chapter-pvecm.html#pvecm_separate_cluster_net_after_creation. All that file does is tell it what IPs to use, they have to exist on the servers already. The file (all /etc/pve) is sync'd to all servers. You might just add the new IP range so it can see both, and then change the servers' IPs...?