Unable to start migration in Plesk: root@203.0.113.2: Permission denied (publickey,gssapi-keyex,gssapi-with-mic, password).

Symptoms

• Migration via SSH key fails with one of the following errors in Tools & Settings > Migration and Transfer Manager:

  PLESK_ERROR: Failed to fetch basic information about resellers, clients and domains data from source servers
  Cause: Command execution failed on the local server with non-zero exit code. command: rsync-r--chmod=Fu=r,Du=rwx,go= --timeout=30 -e 'ssh -i
  /usr/local/psa/var/modules/panel-migrator/sessions/20250121124053/ssh-keys/id_rsa.217.112.92.11 -p 22 -o PasswordAuthentication=no -o
  StrictHostKeyChecking=no -0 GSSAP|Authentication=no' /us/local/psa/admin/plib/modules/panel-migrator/backend/lib/python/parallels/plesk/source/legacy/extras/plesk_12_5_pmm_sh
  ared/root@203.0.113.2:/root/plesk_migrator/plesk_migrator-
  Gikjqhyvo15z9xduwsffal8pnxy96ytf/pmm_agent
  exit code: 255
  stdout:
  stderr: root@203.0.113.2: Permission denied (publickey,gssapi-keyex,gssapi-with-mic, password).
  rsync: connection unexpectedly closed (0 bytes received so far) [sender] rsync error: unexplained error (code 255) at io.c(232) [sender=3.2.7]
  That is a critical error, migration was stopped.

• Trying to access the source server using a ssh RSA key using verbose output in CLI output the following error:
  

  CONFIG_TEXT: debug1: Next authentication method: publickey
  debug1: Offering public key: /root/.ssh/id_rsa RSA SHA256:2e0ABjt0fe9hkGfd9FWqeJyrWzrn5GH3REAGcU4TtnU
  debug1: send_pubkey_test: no mutual signature algorithm

Cause

The SSH key configuration on the Target server is incompatible with the source server.

Resolution

1. Log in to Plesk.

2. Connect to the Plesk server via SSH.

3. Comment the customizations
4. Add the following line to /etc/ssh/ssh_config:

   CONFIG_TEXT: PubkeyAcceptedKeyTypes +ssh-rsa

5. Restart the Migration process.