Unable to create a backup of PostgreSQL database: pg_dump: aborting because of server version mismatch

Symptoms

• The Plesk server has two PostgreSQL database servers installed, with the versions 9.2.15 and 9.5.4.
• One of the databases is created on the PostgreSQL server with version 9.5.4.
• In an attempt to create a backup in Plesk > Tools & Settings > Backup Manager, the process fails with the error below and as result the backup is not created for database that is located on the  PostgreSQL server with version 9.5.4:
  

  CONFIG_TEXT: WARNING: (postgresql object 'admin_db') Failed to execute backup database
  WARNING: (postgresql object 'admin_db') Not all the data was backed up into /var/lib/psa/dumps/domains/example.com/databases/admin_db_4 successfully. pg_dump: server version: 9.5.4; pg_dump version: 9.2.15
  pg_dump: aborting because of server version mismatch

Cause

This is a Plesk bug with the ID #PPPM-5078, which will be fixed in the next Plesk update releases.

Resolution

Until the bug will be fixed, apply the workaround below:

1. Log into the server via SSH.
2. Create a backup for the /etc/psa/psa.conf file:
   

   # cp -a /etc/psa/psa.conf{,.back}

3. Using the vi text editor open the /etc/psa/psa.conf file.
4. Point Plesk to a new PostgreSQL database server by changing the line below from: 
   

   CONFIG_TEXT: PGSQL_DATA_D /var/lib/pgsql/data
   PGSQL_CONF_D /var/lib/pgsql/data
   PGSQL_BIN_D /usr/bin

   To

   CONFIG_TEXT: PGSQL_DATA_D /var/lib/pgsql/9.5/data
   PGSQL_CONF_D /var/lib/pgsql/9.5/data
   PGSQL_BIN_D /usr/pgsql-9.5/bin