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The Basics
Nextcloud Server version (e.g., 29.x.x):
Nextcloud AIO
Operating system and version (e.g., Ubuntu 24.04):
Debian Trixie
Web server and version (e.g, Apache 2.4.25):
Nextcloud AIO
Reverse proxy and version _(e.g. nginx 1.27.2)
nginx
PHP version (e.g, 8.3):
Nextcloud AIO
Is this the first time you’ve seen this error? (Yes / No):
Yes
When did this problem seem to first start?
Today
Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
AIO
Are you using CloudfIare, mod_security, or similar? (Yes / No)
No
Summary of the issue you are facing:
I have a borg repository accessible through SSH and I needed to move it from one server to another one. Now backup does not work anymore. I see the following error:
2025-12-17T10:47:29.616871293Z SSH command line: [‘ssh’, ‘-o’, ‘StrictHostKeyChecking=accept-new’, ‘-i’, ‘/nextcloud_aio_volumes/nextcloud_aio_mastercontainer/data/id_borg’, ‘-p’, ‘8022’, ‘backup@b68.krzm.de’, ‘borg’, ‘serve’, ‘–debug’]
2025-12-17T10:47:29.832280829Z Remote: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
2025-12-17T10:47:29.832353736Z Remote: @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
2025-12-17T10:47:29.832359497Z Remote: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
2025-12-17T10:47:29.832362943Z Remote: IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
2025-12-17T10:47:29.832366059Z Remote: Someone could be eavesdropping on you right now (man-in-the-middle attack)!
2025-12-17T10:47:29.832369244Z Remote: It is also possible that a host key has just been changed.
2025-12-17T10:47:29.832372530Z Remote: The fingerprint for the ED25519 key sent by the remote host is
2025-12-17T10:47:29.832376237Z Remote: SHA256:RRRc0lx+hKtgDK2Rw8rvtC1OGKPnrNSlkabCqqSIh0o.
2025-12-17T10:47:29.832379704Z Remote: Please contact your system administrator.
2025-12-17T10:47:29.832382950Z Remote: Add correct host key in /root/.ssh/known_hosts to get rid of this message.
2025-12-17T10:47:29.832447191Z Remote: Offending ED25519 key in /root/.ssh/known_hosts:3
2025-12-17T10:47:29.832451028Z Remote: Host key for [XXX]:8022 has changed and you have requested strict checking.
2025-12-17T10:47:29.832454184Z Remote: Host key verification failed.
My question: How do I fix that in the borgbackup container of AIO? I have no way of running the container such that I could exec into it and change the known_hosts file.
Steps to replicate it (hint: details matter!):
Move an existing borg repository from one host to another
Okay, I’ve changed the host id of the new server of the one the old server had. Now SSH access works again, but I’ve run into a different problem now:
2025-12-17T11:35:44.384288776Z Did not find borg.config file in the mastercontainer volume.
2025-12-17T11:35:44.385797641Z Cannot create a backup as this is wrong.
I have the same issue and cannot set the remote locations key to the one it had before.
Any idea how to update the borgbackup stored key?
I tried to SSH from the nextcloud server into the remote location.
I said there was a new key and asked me to store it. It is stored ok as I could verify.
Yet Borg seems to have it stored somewhere unknown. There is no borg.config file in /var/lib/docker/volumes/nextcloud_aio_mastercontainer/_data/data/ as I never made a successful backup before
I keep getting the same error:
2026-01-04T17:26:48.736377078Z Your public ssh key for borgbackup is: ssh-ed25519 AAAAC... root@nextcloud-aio-borgbackup
2026-01-04T17:26:49.593769708Z Remote: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
2026-01-04T17:26:49.593803356Z Remote: @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
2026-01-04T17:26:49.593806948Z Remote: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
2026-01-04T17:26:49.593809319Z Remote: IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
2026-01-04T17:26:49.593811708Z Remote: Someone could be eavesdropping on you right now (man-in-the-middle attack)!
2026-01-04T17:26:49.593813930Z Remote: It is also possible that a host key has just been changed.
2026-01-04T17:26:49.593816467Z Remote: The fingerprint for the ED25519 key sent by the remote host is
2026-01-04T17:26:49.593818615Z Remote: SHA256:bzCAy2....
2026-01-04T17:26:49.593820930Z Remote: Please contact your system administrator.
2026-01-04T17:26:49.593823041Z Remote: Add correct host key in /root/.ssh/known_hosts to get rid of this message.
2026-01-04T17:26:49.593825337Z Remote: Offending ECDSA key in /root/.ssh/known_hosts:4
2026-01-04T17:26:49.593827393Z Remote: Host key for 192.168.178.31 has changed and you have requested strict checking.
2026-01-04T17:26:49.593829633Z Remote: Host key verification failed.
2026-01-04T17:26:49.597627994Z Connection closed by remote host. Is borg working on the server?
I am running my Nextcloud instance as an AIO system in a Debian Trixie VM under Proxmox. All containers are up to date (updated yesterday after the presentation of Hub 26: AIO v12.7, Nextcloud 32.0.6)
Later yesterday, I moved the borg repository of my Nextcloud AIO installation to a different LXC container and changed the path to the repo in the AIO GUI. The then manually initiated (from the GUI) backup failed because borg realized the new access path and wanted a „y“ to confirm and to continue. Unfortunately I did not save the log.
Then I started a „borg list“ from the Nextcloud VM-console, entered a „y“ to confirm the new path and it worked. After that I initiated a backup again, it failed with the following log:
2026-02-19T02:01:41.334437670Z Your public ssh key for borgbackup is: ssh-ed25519 AAAAblablabla root@nextcloud-aio-borgbackup 2026-02-19T02:01:42.432737887Z Performing backup... 2026-02-19T02:01:42.432770597Z Did not find borg.config file in the mastercontainer volume. 2026-02-19T02:01:42.432773863Z Cannot create a backup as this is wrong.
I tried the touch /var/lib/docker/volumes/nextcloud_aio_mastercontainer/_data/data/borg.configdescribed above but the dirctory /var/lib/docker/volumes/nextcloud_aio_mastercontainer does not exist.
How can I fix the problem without loosing the backups in the moved Repo?
Additional Info: If I define a path to a repo which does not exist, the backup works. If I switch the path back to the original repo, the old error occurs again:
2026-02-19T02:01:41.334437670Z Your public ssh key for borgbackup is: ssh-ed25519 AAAAblablabla root@nextcloud-aio-borgbackup 2026-02-19T02:01:42.432737887Z Performing backup... 2026-02-19T02:01:42.432770597Z Did not find borg.config file in the mastercontainer volume. 2026-02-19T02:01:42.432773863Z Cannot create a backup as this is wrong.
