Webmin Backup with SSH

Webmin
1
SYSTEM INFORMATION
Ubuntu Linux 24.04.4 REQUIRED
Webmin 2.621 REQUIRED

Hi, I usually work things out but this one is tricky…

Server A = production
Server B = backup server 1
Server C = backup server 2

All are same OS and Webmin version. All runs SSH, same version.
cgnsup = backup user account

Task: To run scheduled backups to B and C from A via SSH

cgnsup has new fresh SSH-keys (ssh-keygen) on all servers. ssh-copy-id works fine.

Now, manual login from A:
$ ssh cgnsup@B = OK
$ ssh cgnsup@C = OK

Now, webmin backup via SSH:
A to B works fine
A to C does not work:

  • scp failed
    …
  • Host key for B has changed and you have requested strict checking.
  • Host key verification failed.

So, from A:

  • why is ssh cgnsup@B working but not the Webmin backup via SSH
  • why is webmin backup to B working bit not to C

A, B and C has the same versions and configurations regarding Webmin and SSH.

Note: There are another (new) server D that Webmin backups via SSH to C works. There are also a Red Hat server E that Webmin backups via SSH to C works. All servers Webmin backups to B works.

2

If you check your /home/cgnsup/.ssh/known_hosts file on C you will see the IP address or FQDN of the servers that have connected.

1 Like
4

Hi, thanks for tip. known_hosts has no readable IP-adresses or domain names. Hmmm… Se .png-file.

known
known1666×366 125 KB

5

This is because your known_hosts file has the connecting IP addresses obfuscated by hashing.

You can use:

ssh-keygen -F <IPAddr>

to see if the IP address exists.

Looking at the man, there’s load of flags associated with this command which might help:

Make sure you have a backup / snapshot or a way in via a console.

6

Hi, some investigations made…

Webmin backup doesn’t work, scp from command line works. I’ve redefined all SSH keys. SSH login is OK cgnsup@192.168.1.63.

THIS IS, according to Webmin debug log, the command - it DOES NOT WORK (on this actual server, webmin backup from this server works to another backup server, same configurations):

cmd=scp -r -P 22 \/tmp/.webmin/backup-20260308_132933.tar.gz cgnsup@192.168.1.63:/bck63/CGN-S08/13.Webmin/cgn-s08-webmin-bck-260308.pl uid= gid=

DOING THIS (the same command) run from command line - THIS WORKS, this is the same server where I’m trying the webmin backup):

scp -r -P 22 /tmp/.webmin/backup/20260308_132933.tar.gz cgnsup@192.168.1.63:/bck63/CGN-S08/13.Webmin/cgn-s08-webmin-bck-260308.pl

So I’ve boiled down the problem to “scp” from the command prompt is working (ssh-keygen works!) but “scp” does not working from Webmin.

It’s a bit confusing.