TrueNAS VM - No network connection - Recover files on VM

I am running TrueNAS Core, version 13.0-U6.2 on an old Turion AMD ProLiant server. If have set up and run a Debian VM to host a weather logging program. This has run for many years with no issues. I also ran NextCloud in a separate jail as a plugin. I recently tried to update this NextCloud plugin and it was there that my problems started!

For some unexplained reason, I am left with a VM that has no network connection. No problem connecting to the TrueNAS on 192.168.1.85 and my router lists the Debian instance with the correct MAC for the NIC but does not issue an IP4 address. It does list the IP6 address.

The result of an ip a is :

My interface set up within TrueNAS is with a bridge as per recommendations on this site :

My /etc/network/interfaces setup is for DHCP :

image

Before I wipe my installation (and possibly migrate to SCALE) I would like to know if there is any way to recover the several years of weather data that are on the Debian VM. I cannot attach a USB as the machine does not support IOMMU. I cannot see any of the volumes outside of the VM, so the files appear to be stuck there.

Any help either on the networking problem or getting the files off the VM would be appreciated.

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Since the VM seems to get an IPv6 can you ping this from another machine?

And if you can ping it is there SSH installed on your Debian machine?

If so my first try in this case would be connecting via SFTP and download the logged data this way.

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Incredibly, this worked! Thank you. I was so focused on the IP4 address problem that I didn’t realise that I could use the IP6 address instead. So, I have recovered my data using WinSCP and proven that the network has partial functionality.

That leaves the issue of why my router is not assigning an IP4 address for the VM. I have tried a different router to handle the DHCP, but that doesn’t seem to solve the issue.

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It would be interesting to know if you have predictable network interface names enabled or not and if there have been distribution upgrades since the VM is older.

Once I recovered the 7 years of weather data, using your IP6 suggestion, I migrated my system to TrueNAS Scale. The Debian VM is running fine, with an IP4 address allocated by DHCP at the router.
Not sure if I had predictable network names enabled on the old system and now unable to check.

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