Solved:
The upgrade to 14.04 did not install sshfs. It's not in the dependencies for deja-dup either, and so its absence led to the behaviour described.
sudo apt-get install sshfs
followed by a reboot of the notebook fixed the issue. Now deja-dup --backup called from the shell results in the backup being sent to the correct location on the server as configured.
For further information on debugging the problem see my answer to the nautilus problem.
Using Ubuntu 19.10, deja-dup 40.1, duplicity 0.8.04.
The questions arise: how comes that deja-dup/duplicity is making up this name?
According to bug reports (ranging as far back as 2010), it's a bug in duplicity affecting deja-dup. Duplicity prefers the fully-qualified domain name (FQDN) for the backup's computer name.
- The way the FQDN lookup is performed is affected by both your computer's network configuration, and the way the network the computer is connected to behaves.
- In particular, external network changes can therefore break backups.1 This includes moving the computer from one network to another.
See
how to fix this?
The bug reports hints at editing /etc/hosts in various ways. Here's what I changed, with mycomputer being my chosen name. Note that order seems to matter.
/etc/hosts (ipv6 addresses omitted)
Original:
127.0.0.1 localhost
127.0.1.1 mycomputer
Modified:
127.0.0.1 mycomputer localhost
127.0.1.1 mycomputer
As soon as I saved the file, an automatic backup started. It worked as expected.2,3
See
1 My backups broke around the time when my ISP upgraded their infrastructure in my area to ipv6. Started seeing "hostnamed changed" with hostnames such as dynamic-xxxx-yyyy-zzzz.area-123.example.com.
2 Tried to verify by reverting the file and rebooting, but backup still works so unsure if it actually fixes the problem, or just triggers deja-dup/duplicity "the right way". Might be related to DHCP timeouts (7 days) in the ISP-owned router, or some other setting I changed. Am posting the answer anyways, but might have to revise if it stops working in a week.3
3 It has now been more than one week since writing this answer.2 Both starting a backup and verifying backups succeeded. Also rebooted and started another backup, which also succeeded. It seems the suggested fix works so far, at least for myself on my machine and in my network environment.
Best Answer
I had changed my hostname in
/etc/hostnamebut I forgot to change it in/etc/hosts. Edit hosts file so that it matches hostname and duplicity is all better.