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Article ID: 123700, created on Nov 27, 2014, last review on Nov 27, 2014

  • Applies to:
  • Plesk Automation 11.5


Adding new service node failed with error:

'SSH communication error: Username/PublicKey combination invalid'


  1. While adding new service node was used login name different from root.

  2. Was used corrupted pair public/private keys or public key was not copied on service node.


For adding new service node using private key perform the following steps:

  1. Log in to Parallels Plesk Automation (PPA) Management node.

  2. Generate new public and private keys pair with the command:

    [root@ppa ~]# ssh-keygen -b 1024 -t dsa

    Follow the instructions. Set the path to files (or leave it by default) and passphrase for the key.

    Generating public/private dsa key pair.
    Enter file in which to save the key (/root/.ssh/id_dsa):
    Enter passphrase (empty for no passphrase):
    Enter same passphrase again:
    Your identification has been saved in /root/.ssh/id_dsa.
    Your public key has been saved in /root/.ssh/
    The key fingerprint is:
  3. Make sure the keys were created:

    [root@ppa ~]# ll .ssh/
    total 16
    -rw------- 1 root root 612 Dec 18 04:11 authorized_keys
    -rw------- 1 root root 744 Dec 18 05:18 id_dsa #private
    -rw-r--r-- 1 root root 608 Dec 18 05:18 #public
    -rw-r--r-- 1 root root 394 Dec 18 04:05 known_hosts 
  4. Copy the public key to the adding service node with using command:

    [root@ppa ~]# scp .ssh/ root@ 

    Note: The colon symbol means that the file will be copied in user's home folder (change it if required).

  5. Log in to adding service node and perform the following actions:

       cat >> .ssh/authorized_keys
       chmod 700 .ssh
       chmod 600 .ssh/authorized_keys
  6. Log in to Parallels Plesk Automation (PPA) Administraton Panel and new service node in Top -> Infrastructure -> Service nodes -> Add New Node.

  7. Enter root login, select the file '**id_dsa**' as the private key and enter the passphrase you set when generated the keys as the private key password.

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