Installed minimal debian image on my rPI5B.  Then used "armbian-config --cmd PVE001" to install Proxmox.  That went well with no reported errors.

 

Navigated to the Proxmox web GUI and it looked and acted as expected.  I currently have an AMD64 Proxmox cluster operating on my homelab so I am familiar with Proxmox.

 

I wanted to make some changes to my network configuration using the Proxmox GUI.  When I clicked the "Apply Configuration" button, it threw an "incompatible ifupdown2 package version" instead of applying the configuration.

 

Edited August 18Aug 18 by tsimblist
fix markup

I see on my NanoPi-R6C, which runs Armbian Trixie userspace:

# apt list | grep ifupdown
ifupdown-extra/unstable,stable 0.34 all
ifupdown-multi/unstable,stable 1.0.0 all
ifupdown-ng-compat/stable 0.12.1-7 all
ifupdown-ng/stable 0.12.1-7 arm64
ifupdown2/unstable,stable 3.0.0-1.3 all
ifupdown/stable,now 0.8.44+deb13u1 arm64 [installed,automatic]

From raspbian/debian Bookworm from RPL I know package ifupdown is not installed/included. Their Trixie is forced netplan.io as well, but if vanilla Debian, ifupdown is not needed if you just use NetworkManager to do networking. I have used in-place dist-upgrades for many years, so for most Debian systems I already purged the ifupdown package or went to systemd-networkd for more headless/unattended.

At least NM only is perfectly fine for having a bridge with enslaved physical ethernet ports so that you can run KVM/libvirtd/QEMU with fixed (or spoofed) known HW MAC address so you can even have the installed Linux from old (broken) computer/SBC easily as VM and keep whole LAN or VLAN etc the same. I do not know what ifupdown2 is. Maybe it is due to netplan.io that is also used in Armbian Trixie fresh images.

Only thing from this topic I currently see is that I need to cleanup that originally Armbian Bookworm on the my NanoPi-R6C so that it does not have/use ifupdown package, same as I already have done on an RPI4 that runs various VMs. I don't know why/if Proxmox maybe needs ifupdown2, I just use standard distro KVM/libvirtd/QEMU for years already on Aarch64 boards and works good/flexible enough for me. Proxmox also uses same KVM/libvirtd/QEMU underneath so I guess could be treated the same as a virt-manager/virsh operated system. NM also has it own internal ifupdown AFAIR, see its config for more info, I haven't touched it myself.

Edited August 18Aug 18 by eselarm

Thank you for your reply.  It helped me review my assumptions.  Like I assumed that this was an Armbian issue because it didn't properly install/upgrade the ifupdown2 package from the Proxmox repo.  But I was unable to list that package from that repo.  It only appeared in the Debian repo.

 

So I loaded the Proxmox VE ARM installer ISO into an Ubuntu VM that I had in my homelab and found the missing package and copied it to the RPI5B and installed it.  Problem solved.

 

Thank you for your support.

7 hours ago, eselarm said:

Trixie is forced netplan.io as well,

Thank you for the heads up.  I had to shutdown netplan so that Proxmox could use /etc/network/interfaces for the network configuration.

1 hour ago, tsimblist said:

had to shutdown netplan so that Proxmox could use /etc/network/interfaces

Yes my worry with your setup is that there are potentially 3 tools dealing with the network: ifupdown, netplan, NetworkManager

Netplan does configs for NetworkManager (and systemd-networkd) via yaml files but is not aware of old/legacy ifupdown maybe. And it seem Proxmox want to cover a wider range of releases and maybe distros, so it seems it does its thing via ifupdown2. I think you should simplify things w.r.t. networking, else you risk off-line situations for your RPi5 and including the VMs on it. I used also pihole and router as VM, I had once an issue with networking, and it gets very nasty and a small disaster if I cannot get things up and running again. So I have a serial USB-TTL cable connected to my RPi4 now, so that with a laptop directly connected to it, I am able to fix networking on the CLI, only by using nmcli. 

 

In your case, I would see if Proxmox can do things the strictly/native Debian Trixie way, so maybe do a test and tryrun:

apt purge --autoremove ifupdown2 netplan.io

If that looks like the whole thing would not work anymore, cancel. But as I indicated, I did this command and networking still isall OK. But no Proxmox, I use virt-manager or also directly edit config (.xml) files for VMs as well.

Edited August 18Aug 18 by eselarm

I agree about simplifying my network setup.  Proxmox has leveraged the /etc/network/interfaces file for some serious networking functionality.  It defaults to a simple network with a Linux bridge for virtual nics.  As my homelab grew, I moved to Open vSwitch which uses the same Web GUI page and interfaces file underneath.  Now Proxmox has Software-Defined Network which I should probably migrate to given I currently have eight servers in a cluster with the RPi5 tentatively making number nine.  It appears they are still using /etc/network/interfaces with SDN.

 

All of my AMD64 homelab servers were loaded with Proxmox VE installer ISOs.  Proxmox uses Ubuntu Linux kernels for the ZFS support, Debian user space and the Proxmox VE hypervisor for KVM/QEMU, LXC and the Web GUI.. I had intended to do the same thing for my RPi5 using this guide:  Install Proxmox ARM64 on a Raspberry Pi 5 This Weekend  That's why I bought the RPi5 in the first place.

 

But it did not work for me as advertised, so I found Armbian which got me so much farther down the road along with better functionality.  However I do have to troubleshoot things like networking config conflicts and ZFS not working.

 

I also use serial consoles for most of my servers for the same reason, a way to fix network problems when the Web GUI is down.