Unable to reload DNS service on Plesk server: invalid command from 127.0.0.1#41838: bad auth

Symptoms

• Some DNS records are not propagated automatically. Manual DNS service restart resolves this issue.

• Unable to reload the DNS service:

  # service bind9 reload
  
  Job for bind9.service failed because the control process exited with error code. See "systemctl status bind9.service" and "journalctl -xe" for details.

• The next rows appear in the /var/log/syslog or /var/log/messages files in an attempt to reload the DNS service:

  CONFIG_TEXT: systemd[1]: Reloading BIND Domain Name Server.
  named[24013]: invalid command from 127.0.0.1#41838: bad auth
  rndc[24290]: rndc: connection to remote host closed
  rndc[24290]: This may indicate that
  rndc[24290]: * the remote server is using an older version of the command protocol,
  rndc[24290]: * this host is not authorized to connect,
  rndc[24290]: * the clocks are not synchronized,
  rndc[24290]: * the key signing algorithm is incorrect, or
  rndc[24290]: * the key is invalid.
  systemd[1]: bind9.service: Control process exited, code=exited status=1
  systemd[1]: Reload failed for BIND Domain Name Server.

• There are two different keys specified in the /etc/named.conf and /etc/bind/rndc.key (or /etc/rndc.key) files:

  # /etc/named.conf
  
  key "rndc-key" {
  algorithm hmac-md5;
  secret "CeMgS**********yv0x40Q==";
  };

  # cat /etc/bind/rndc.key
  
  key "rndc-key" {
  algorithm hmac-md5;
  secret "aff2YA**********FRkj/g==";
  };

Cause

Two different keys are in conflict with each other.

Resolution

Use the same key in both files:

1. Connect to the server via SSH.

2. Get the key from the /etc/bind/rndc.key (or /etc/rndc.key) file and copy it.

   # cat /etc/bind/rndc.key
   
   key "rndc-key" {
   algorithm hmac-md5;
   secret "aff2YA**********FRkj/g==";
   };

3. Open the /etc/named.conf and/or /etc/bind/rndc.conf file via any text editor and modify change the key to the correct one received from the previous step:

   CONFIG_TEXT: [BEFORE]
   
   key "rndc-key" {
   algorithm hmac-md5;
   secret "CeMgS**********yv0x40Q==";
   };

   CONFIG_TEXT: [AFTER]
   
   key "rndc-key" {
   algorithm hmac-md5;
   secret "aff2YA**********FRkj/g==";
   };

4. Restart the DNS service:

   # service bind9 restart

   OR

   # service named-chroot restart