Can't access via SSH or web interface after upgrade to 7.0

[bigjoedata]

Hoping for help here.
I have been running Proxmox for a while now, at least a couple years, I can't remember if I started with 5.x or 6.x but have updated regularly. I upgraded to 7.0 from 6.4 but now I can't ssh in, or access via web interface (internal ip:8006). I followed the standard upgrade instructions , and did "apt install ifupdown2 (not sure if this was a good idea or not)" and rebooted prior to installation. The upgrade seemed to go successfully but now am locked out. Some notes:

1) I can ping successfully

2) When I try to ssh to root@ip, I get an error "kex_exchange_identification: read: Connection reset by peer".

3) When I try to access via web interface, I get error "ERR_CONNECTION_RESET" in Chrome.

4) I normally use my computer headless with GPU passthrough so the hdmi output doesn't appear locally from a monitor. I couldn't figure out how to disable the GPU passthrough from GRUB so can't troubleshoot very well locally.

5) I have also tried rebooting my router for good measure

Any suggestions are greatly appreciated!

 

[chrcoluk]

Whatever the fix may be to get you back to where you were, you going to need some form of console access.

If getting that is excessively hard, you could boot with a rescue os, then mount the root filesystem to see if anything looks off in the configuration.