1. Installation  - as usual:

[root@cld-foreman ~]# wget http://ftp-stud.hs-esslingen.de/pub/epel//6/x86_64/epel-release-6-8.noarch.rpm
[…]
[root@cld-foreman ~]# yum install puppet-server puppet foreman-installer mysql mysql-devel ruby-mysql rubygem-activerecord mod_ssl -y
[…]

2. Before using l foreman-installer - create foreman DB and GRANT to foreman user:

[root@mysql-cluster-01 ~]# mysql -u root
mysql> create database foreman;
mysql> grant all privileges on foreman.* to 'foreman'@'cld-foreman%' identified by 'XXXXXXXX';
mysql> flush privileges;
mysql> commit;

3. Run installer:
[root@cld-foreman ~]# foreman-installer -i
[…]
Parameter dhcp_gateway (of module foreman_proxy)
DHCP pool gateway
current value: 192.168.100.1
new value:
192.168.60.254

Parameter dns_server (of module foreman_proxy)
Address of DNS server to manage
current value: 127.0.0.1
new value:
192.84.143.16 -> 192.168.60.254 (as recommended by Fulvia "DNS for the private network")

Parameter dns_reverse (of module foreman_proxy)
DNS reverse zone name
current value: 100.168.192.in-addr.arpa
new value:
60.168.192.in-addr.arpa

Parameter db_host (of module foreman)
Database 'production' host
current value: 
new value:
mysql-cluster.cloud.pd.infn.it

Parameter db_type (of module foreman)
Database 'production' type (valid types:
mysql/postgresql/sqlite)
current value: postgresql
new value:
mysql

Parameter db_port (of module foreman)
Database 'production' port
current value: 
new value:
3306

Parameter db_database (of module foreman)
Database 'production' database (e.g. foreman)
current value: 
new value:
foreman

[…]
Installing             -#tice: /passenvar/lib/tf=                                      [25%] [........                Could not prefetch mysql_grant provider 'mysql': Execution of '/usr/bin/mysql --defaults-file=/root/.my.cnf -NBe SHOW GRANTS FOR root@cld-foreman.cloud.pd.infn.it;' returned 1: ERROR 1064 (42000) at line 1: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-foreman.cloud.pd.infn.it' at line 1

4. GRANT also for user "root":
[root@mysql-cluster-01 ~]# mysql -u root
mysql>grant all privileges on *.* to 'root'@'cld-foreman%' with grant option;

5. Rereun foreman-installer ->/var/log/httpd/error_log errors:
Access denied for user 'foreman'@'ha-proxy-01' (using password: YES) (Mysql2::Error)

6. Other GRANTS - the access to the DB is from the various ha-proxies:
mysql> GRANT ALL ON foreman.* TO 'foreman'@'ha-proxy-01' IDENTIFIED BY
'XXXXXXXXXX';
mysql> GRANT ALL ON foreman.* TO 'foreman'@'ha-proxy-02' IDENTIFIED BY
'XXXXXXXXXX';
mysql> GRANT ALL ON foreman.* TO 'foreman'@'ha-proxy-03' IDENTIFIED BY
'XXXXXXXXXX';
mysql> FLUSH PRIVILEGES;
mysql> commit;

7. STILL errors - /var/log/httpd/error_log:
Host 'ha-proxy-01' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts' (Mysql2::Error)

8. On all HA proxy (ha-proxy-01, ha-proxy-02, ha-proxy-03) in /etc/my.cnf set variable:
max_connect_errors=30000

Reboot ALL hosts - check max_connect_errors remains 30000

9. Rerun foreman-installer - /var/log/httpd/error_log ho trovato:
Mysql2::Error: Table 'foreman.features' doesn't exist: SHOW FULL FIELDS FROM `features` (ActiveRecord::StatementInvalid)

10. Content of DB:
[root@cld-foreman ~]# mysql -u foreman -p -h mysql-cluster.cloud.pd.infn.it
Enter password: 
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| foreman            |
+--------------------+
2 rows in set (0.00 sec)

mysql> use foreman;
Database changed
mysql> show tables;
Empty set (0.00 sec)

10 Rerun foreman-installer and change the DNS as recommended by Fulvia, no errors in all logs - SUCCESS:
Installing             Done                                               [100%] [.......................................]
  Success!
  * Foreman is running at
https://cld-foreman.cloud.pd.infn.it
      Default credentials are 'admin:changeme'
  * Foreman Proxy is running at
https://cld-foreman.cloud.pd.infn.it:8443
  * Puppetmaster is running at port 8140
  The full log is at
/var/log/foreman-installer/foreman-installer.log

11. Content of DB:
[root@cld-foreman ~]# mysql -u foreman -p -h mysql-cluster.cloud.pd.infn.it
Enter password: 
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| foreman            |
| test               |
+--------------------+
3 rows in set (0.00 sec)

mysql> use foreman;
mysql> show tables;
+-----------------------------------+
| Tables_in_foreman                 |
+-----------------------------------+
| architectures                     |
| architectures_operatingsystems    |
| audits                            |
| auth_sources                      |
| bookmarks                         |
| compute_resources                 |
| config_templates                  |
| config_templates_operatingsystems |
| domains                           |
| environment_classes               |
| environments                      |
| fact_names                        |
| fact_values                       |
| features                          |
| features_smart_proxies            |
| host_classes                      |
| hostgroup_classes                 |
| hostgroups                        |
| hosts                             |
| images                            |
| key_pairs                         |
| locations_organizations           |
| logs                              |
| lookup_keys                       |
| lookup_values                     |
| media                             |
| media_operatingsystems            |
| messages                          |
| models                            |
| nics                              |
| notices                           |
| operatingsystems                  |
| operatingsystems_ptables          |
| operatingsystems_puppetclasses    |
| os_default_templates              |
| parameters                        |
| ptables                           |
| puppetclasses                     |
| reports                           |
| roles                             |
| schema_migrations                 |
| sessions                          |
| settings                          |
| smart_proxies                     |
| sources                           |
| subnet_domains                    |
| subnets                           |
| taxable_taxonomies                |
| taxonomies                        |
| template_combinations             |
| template_kinds                    |
| tokens                            |
| trend_counters                    |
| trends                            |
| user_compute_resources            |
| user_domains                      |
| user_facts                        |
| user_hostgroups                   |
| user_notices                      |
| user_roles                        |
| usergroup_members                 |
| usergroups                        |
| users                             |
+-----------------------------------+
63 rows in set (0.01 sec)

12. NO connection to the web interface!!!!