Locked out of Proxmox after network changes

[SnapshotNinja]

Hi everyone,


I seem to have accidentally locked myself out of my Proxmox setup during some network configuration testing, and I am not sure how to recover access.


I have two VMs: a headless Debian VM and a TrueNAS VM. I was troubleshooting some TrueNAS connectivity issues that appeared to be related to NAT. During testing, I removed the vmbr0 network device from the TrueNAS VM and added a PCI device for the Ethernet or network controller instead. I assumed this would help based on advice I received elsewhere.


After applying the change, I rebooted the Proxmox host. As soon as it restarted, nothing would boot properly. Proxmox did not load, and neither of my VMs started. I also lost SSH access to both the host and the VMs.


I then connected a keyboard and monitor directly to my UGreen NAS DXP2800, since it has HDMI out. No matter which of the two Proxmox boot entries I select, Proxmox appears to start loading but then immediately reboots. After that, it loads directly into the TrueNAS shell instead of the Proxmox host shell. The TrueNAS console does not respond to any of the number key options, but it does react to CTRL+ALT+DEL, which reboots the system.


Next, I tried using my Proxmox USB installer to enter rescue mode. However, I was met with the error shown in the image attached to this post. Even if rescue mode had loaded correctly, I am not sure what steps I would need to take to fix the issue.


For additional context, Proxmox is installed on this UGreen DXP2800 NAS as a ZFS RAID1 across the two NVMe drives.


I would really appreciate help or guidance on how to recover Proxmox and restore access to the host.


Thanks in advance!

 

[odhiambo]

Hello @SnapshotNinja,

Sorry for what happened. I can understand how frustrating this can get.
Let me try to help you from the top of my head, given that you either did not attach anything to the post or it just disappeared. This is my first post here. I am very new to the forum.

So, if there was a network change, what was the change? Did you change the IP subnet on your router? Even if you did, that should not make Proxmox not boot. It will not be accessible, but booting it will boot normally.
Secondly, a VM cannot make the node to not boot. No.

Let us fix the network issue on the Proxmox host (aka Node) before dealing with the VMs.
1. With a monitor, keyboard and mouse attached to the machine on which Proxmox is installed, you should see a login prompt.
Enter username (root) and the associated password. Enter to login.
(a) Type the command ```ip a``` and enter. You will see something like this:

root@pve:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host noprefixroute
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master vmbr0 state UP group default qlen 1000
link/ether NN:NN:NN:NN:NN:NN brd ff:ff:ff:ff:ff:ff
altname enxXXXXXXXXXXXX

You are interested in the nam eof the 2nd network device. Mine is enp2s0.
And while at it, let me know what the name of the 3nd device is. Mine is vmbr0 - the node's bridge interface. Does it have an IP address from your router?
If it is not present at all, we can manually get it created. If it is there, but with the wrong IP address, we can fix that as well:

(b) Run this command: ``` nano /etc/network/interfaces```

You should see something like this below:
```
[...]
auto vmbr0
iface vmbr0 inet static
address 192.168.69.10/24 # Here change the IP to match what you want, within your current subnet
gateway 192.168.69.1 # Change this gateway IP address to the IP of your router
bridge-ports enp2s0 # Here, change the enp2s0 to what you gleaned from the `ip a` command above - the #2 interface
bridge-stp off
bridge-fd 0
[...]

```

Save the file and reboot.
That fixes the network issue with the PVE node. You should be able to access it with the new IP address after the reboot.
After that, come back so that we can fix the VMs network issues.

HTH