Migration does not start from the source server powered by ubuntu 14: Permission denied (publickey,password).

Symptoms

• Panel migrator fails to connect to the source server with the following error:

  PLESK_ERROR: rsync -r --chmod=Fu=r,Du=rwx,go= --timeout=30 -e 'ssh -i /usr/local/psa/var/modules/panel-migrator/sessions/20230413103231/ssh-keys/id_rsa.203.0.113.2 -p 22 -o PasswordAuthentication=no -o StrictHostKeyChecking=no -o GSSAPIAuthentication=no' /usr/local/psa/admin/plib/modules/panel-migrator/backend/lib/python/parallels/plesk/source/legacy/extras/plesk_17_0_pmm_shared/ root@203.0.113.2:/root/plesk_migrator/plesk_migrator-7n8mjdgnt0o95xajhwso9z5ax0m6xktz/pmm_agent
  Warning: Identity file /usr/local/psa/var/modules/panel-migrator/sessions/20230413103231/ssh-keys/id_rsa.203.0.113.2 not accessible: No such file or directory.
  root@203.0.113.2: Permission denied (publickey,password).
  rsync: connection unexpectedly closed (0 bytes received so far) [sender]
  rsync error: unexplained error (code 255) at io.c(231) [sender=3.2.7]

• Source server is running Ubuntu 14

Cause

Ubuntu 14 doesn't support encryption algorithms compatible with SSH keys used by default on modern operating systems.

Resolution

1. Connect to the target server via SSH

2. Generate a ed25519 key:

   # cd /root/.ssh && ssh-keygen -t ed25519

3. Push the content of the generated public key *.pub to the /root/.ssh/authorized_keys file on the source server

4. Update the migrator's config.ini, so it'll use key instead of password for the ssh auth:

   # egrep -iE '(\[s|^ssh)' /opt/psa/var/modules/panel-migrator/sessions/20230413103231/config.ini
   [source]
   ssh-username = "root"
   ssh-auth-type = "key"
   ssh-port = "22"
   ssh-key = "/root/.ssh/migration"