Once the Cluster is installed, we can check what was done. You will notice that the: mysqld is already running with the vendor implementation you have chosen (in our case: MariaDB) You should be able to connect to the database using the root password which you provided during the cluster installation:

[root@galera-mysql1 mysql]# mysql -uroot -p
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 61
Server version: 10.2.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]>
MariaDB [(none)]>
MariaDB [(none)]>
MariaDB [(none)]>
MariaDB [(none)]> l
    -> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'l' at line 1
MariaDB [(none)]> \l
ERROR: Unknown command '\l'.
    -> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '\l' at line 1
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
+--------------------+
3 rows in set (0.00 sec)

Of course, we can create new database and check the consistency between the servers:

MariaDB [(none)]>
MariaDB [(none)]> create database testRepl;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> use testRepl
Database changed
MariaDB [testRepl]> create table employees(id int, name varchar(20));
Query OK, 0 rows affected (0.00 sec)

MariaDB [testRepl]> insert into employees values(1,'Julien');
Query OK, 1 row affected (0.00 sec)

MariaDB [testRepl]> commit;
Query OK, 0 rows affected (0.00 sec)

MariaDB [testRepl]> select * from employees;
+------+--------+
| id   | name   |
+------+--------+
|    1 | Julien |
+------+--------+
1 row in set (0.00 sec)

MariaDB [testRepl]>
MariaDB [testRepl]>

Same should be available from the 2nd node:

[root@galera-mysql2 ~]# mysql -uroot -p
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 17
Server version: 10.2.17-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| testRepl           |
+--------------------+
4 rows in set (0.00 sec)

MariaDB [(none)]> use testRepl;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [testRepl]> show tables;
+--------------------+
| Tables_in_testRepl |
+--------------------+
| employees          |
+--------------------+
1 row in set (0.00 sec)

MariaDB [testRepl]> select * from employees;
+------+--------+
| id   | name   |
+------+--------+
|    1 | Julien |
+------+--------+
1 row in set (0.00 sec)

MariaDB [testRepl]>
MariaDB [testRepl]>

#
# my.cnf template for clustercontroller
# Copyright (C) 2011-2015 severalnines.com
#

[MYSQLD]
user=mysql
basedir=/usr/
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
pid_file=/var/lib/mysql/mysql.pid
port=3306
log_error=/var/log/mysql/mysqld.log
log_warnings=2
# log_output = FILE

#Slow logging
slow_query_log_file=/var/log/mysql/mysql-slow.log
long_query_time=2
slow_query_log=OFF
log_queries_not_using_indexes=OFF

### INNODB OPTIONS
innodb_buffer_pool_size=746M
innodb_flush_log_at_trx_commit=2
innodb_file_per_table=1
innodb_data_file_path = ibdata1:100M:autoextend
## You may want to tune the below depending on number of cores and disk sub
innodb_read_io_threads=4
innodb_write_io_threads=4
innodb_doublewrite=1
innodb_log_file_size=256M
innodb_log_buffer_size=32M
innodb_buffer_pool_instances=1
innodb_log_files_in_group=2
innodb_thread_concurrency=64
# innodb_file_format = barracuda
innodb_flush_method = O_DIRECT
# innodb_locks_unsafe_for_binlog = 1
innodb_autoinc_lock_mode=2
## avoid statistics update when doing e.g show tables
innodb_stats_on_metadata=0
default_storage_engine=innodb

# CHARACTER SET
# collation_server = utf8_unicode_ci
# init_connect = 'SET NAMES utf8'
# character_set_server = utf8

# REPLICATION SPECIFIC
server_id=1
binlog_format=ROW
# log_bin = binlog
# log_slave_updates = 1
# gtid_mode = ON
# enforce_gtid_consistency = 1
# relay_log = relay-bin
# expire_logs_days = 7

# OTHER THINGS, BUFFERS ETC
# key_buffer_size = 24M
tmp_table_size = 64M
max_heap_table_size = 64M
max_allowed_packet = 512M
# sort_buffer_size = 256K
# read_buffer_size = 256K
# read_rnd_buffer_size = 512K
# myisam_sort_buffer_size = 8M
skip_name_resolve
memlock=0
sysdate_is_now=1
max_connections=500
thread_cache_size=512
query_cache_type = 0
query_cache_size = 0
table_open_cache=1024
lower_case_table_names=0
# 5.6 backwards compatibility (FIXME)
# explicit_defaults_for_timestamp = 1
##
## WSREP options
##

performance_schema = OFF
performance-schema-max-mutex-classes = 0
performance-schema-max-mutex-instances = 0

# Full path to wsrep provider library or 'none'
wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_on=ON
wsrep_node_address=192.168.0.100

# Provider specific configuration options
wsrep_provider_options="base_port=4567; gcache.size=1024M; gmcast.segment=0 "

# Logical cluster name. Should be the same for all nodes.
wsrep_cluster_name="my_wsrep_cluster"

# Group communication system handle
wsrep_cluster_address=gcomm://192.168.0.100,192.168.0.101

# Human_readable node name (non-unique). Hostname by default.
wsrep_node_name=192.168.0.100

# Address for incoming client connections. Autodetect by default.
#wsrep_node_incoming_address=

# How many threads will process writesets from other nodes
wsrep_slave_threads=4

# DBUG options for wsrep provider
#wsrep_dbug_option

# Generate fake primary keys for non-PK tables (required for multi-master
# and parallel applying operation)
wsrep_certify_nonPK=1

# Location of the directory with data files. Needed for non-mysqldump
# state snapshot transfers. Defaults to mysql_real_data_home.
#wsrep_data_home_dir=

# Maximum number of rows in write set
wsrep_max_ws_rows=131072

# Maximum size of write set
wsrep_max_ws_size=1073741824

# to enable debug level logging, set this to 1
wsrep_debug=0

# convert locking sessions into transactions
wsrep_convert_LOCK_to_trx=0

# how many times to retry deadlocked autocommits
wsrep_retry_autocommit=1

# change auto_increment_increment and auto_increment_offset automatically
wsrep_auto_increment_control=1

# replicate myisam
wsrep_replicate_myisam=1

# retry autoinc insert, which failed for duplicate key error
wsrep_drupal_282555_workaround=0

# enable "strictly synchronous" semantics for read operations
wsrep_causal_reads=0

# Command to call when node status or cluster membership changes.
# Will be passed all or some of the following options:
# --status  - new status of this node
# --uuid    - UUID of the cluster
# --primary - whether the component is primary or not ("yes"/"no")
# --members - comma-separated list of members
# --index   - index of this node in the list
#wsrep_notify_cmd=

##
## WSREP State Transfer options
##

# State Snapshot Transfer method
# ClusterControl currently DOES NOT support wsrep_sst_method=mysqldump
wsrep_sst_method=mariabackup

# Address on THIS node to receive SST at. DON'T SET IT TO DONOR ADDRESS!!!
# (SST method dependent. Defaults to the first IP of the first interface)
#wsrep_sst_receive_address=

# SST authentication string. This will be used to send SST to joining nodes.
# Depends on SST method. For mysqldump method it is root:<root password>
# IMPORTANT: The user/password in wsrep_sst_auth must match
# user/password in [xtrabackup]


# Desired SST donor name.
#wsrep_sst_donor=

# Protocol version to use
# wsrep_protocol_version=

# log conflicts
wsrep_log_conflicts=1

[MYSQL]
socket=/var/lib/mysql/mysql.sock
# default_character_set = utf8
[client]
socket=/var/lib/mysql/mysql.sock
# default_character_set = utf8

[mysqldump]
max_allowed_packet = 512M
# default_character_set = utf8



# IMPORTANT: The user/password in wsrep_sst_auth must match
# user/password in [xtrabackup]
[xtrabackup]
databases-exclude=lost+found
ssl_mode=DISABLED




[MYSQLD_SAFE]
# log_error = /var/log/mysqld.log
basedir=/usr/
# datadir = /var/lib/mysql

!include /etc/my.cnf.d/secrets-backup.cnf
[root@galera-mysql1 mysql]# cat /etc/my.cnf.d/secrets-backup.cnf
# Security credentials for backup.
[mysqldump]
user=backupuser
password=eZJ8Av8ryRWl9h0B

[xtrabackup]
user=backupuser
password=eZJ8Av8ryRWl9h0B

[mysqld]
wsrep_sst_auth=backupuser:eZJ8Av8ryRWl9h0B

#
# my.cnf template for clustercontroller
# Copyright (C) 2011-2015 severalnines.com
#

[MYSQLD]
user=mysql
basedir=/usr/
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
pid_file=/var/lib/mysql/mysql.pid
port=3306
log_error=/var/log/mysql/mysqld.log
log_warnings=2
# log_output = FILE

#Slow logging
slow_query_log_file=/var/log/mysql/mysql-slow.log
long_query_time=2
slow_query_log=OFF
log_queries_not_using_indexes=OFF

### INNODB OPTIONS
innodb_buffer_pool_size=746M
innodb_flush_log_at_trx_commit=2
innodb_file_per_table=1
innodb_data_file_path = ibdata1:100M:autoextend
## You may want to tune the below depending on number of cores and disk sub
innodb_read_io_threads=4
innodb_write_io_threads=4
innodb_doublewrite=1
innodb_log_file_size=256M
innodb_log_buffer_size=32M
innodb_buffer_pool_instances=1
innodb_log_files_in_group=2
innodb_thread_concurrency=64
# innodb_file_format = barracuda
innodb_flush_method = O_DIRECT
# innodb_locks_unsafe_for_binlog = 1
innodb_autoinc_lock_mode=2
## avoid statistics update when doing e.g show tables
innodb_stats_on_metadata=0
default_storage_engine=innodb

# CHARACTER SET
# collation_server = utf8_unicode_ci
# init_connect = 'SET NAMES utf8'
# character_set_server = utf8

# REPLICATION SPECIFIC
server_id=2
binlog_format=ROW
# log_bin = binlog
# log_slave_updates = 1
# gtid_mode = ON
# enforce_gtid_consistency = 1
# relay_log = relay-bin
# expire_logs_days = 7

# OTHER THINGS, BUFFERS ETC
# key_buffer_size = 24M
tmp_table_size = 64M
max_heap_table_size = 64M
max_allowed_packet = 512M
# sort_buffer_size = 256K
# read_buffer_size = 256K
# read_rnd_buffer_size = 512K
# myisam_sort_buffer_size = 8M
skip_name_resolve
memlock=0
sysdate_is_now=1
max_connections=500
thread_cache_size=512
query_cache_type = 0
query_cache_size = 0
table_open_cache=1024
lower_case_table_names=0
# 5.6 backwards compatibility (FIXME)
# explicit_defaults_for_timestamp = 1
##
## WSREP options
##

performance_schema = OFF
performance-schema-max-mutex-classes = 0
performance-schema-max-mutex-instances = 0

# Full path to wsrep provider library or 'none'
wsrep_provider=/usr/lib64/galera/libgalera_smm.so
wsrep_on=ON
wsrep_node_address=192.168.0.101

# Provider specific configuration options
wsrep_provider_options="base_port=4567; gcache.size=1024M; gmcast.segment=0 "

# Logical cluster name. Should be the same for all nodes.
wsrep_cluster_name="my_wsrep_cluster"

# Group communication system handle
wsrep_cluster_address=gcomm://192.168.0.100,192.168.0.101

# Human_readable node name (non-unique). Hostname by default.
wsrep_node_name=192.168.0.101

# Address for incoming client connections. Autodetect by default.
#wsrep_node_incoming_address=

# How many threads will process writesets from other nodes
wsrep_slave_threads=4

# DBUG options for wsrep provider
#wsrep_dbug_option

# Generate fake primary keys for non-PK tables (required for multi-master
# and parallel applying operation)
wsrep_certify_nonPK=1

# Location of the directory with data files. Needed for non-mysqldump
# state snapshot transfers. Defaults to mysql_real_data_home.
#wsrep_data_home_dir=

# Maximum number of rows in write set
wsrep_max_ws_rows=131072

# Maximum size of write set
wsrep_max_ws_size=1073741824

# to enable debug level logging, set this to 1
wsrep_debug=0

# convert locking sessions into transactions
wsrep_convert_LOCK_to_trx=0

# how many times to retry deadlocked autocommits
wsrep_retry_autocommit=1

# change auto_increment_increment and auto_increment_offset automatically
wsrep_auto_increment_control=1

# replicate myisam
wsrep_replicate_myisam=1

# retry autoinc insert, which failed for duplicate key error
wsrep_drupal_282555_workaround=0

# enable "strictly synchronous" semantics for read operations
wsrep_causal_reads=0

# Command to call when node status or cluster membership changes.
# Will be passed all or some of the following options:
# --status  - new status of this node
# --uuid    - UUID of the cluster
# --primary - whether the component is primary or not ("yes"/"no")
# --members - comma-separated list of members
# --index   - index of this node in the list
#wsrep_notify_cmd=

##
## WSREP State Transfer options
##

# State Snapshot Transfer method
# ClusterControl currently DOES NOT support wsrep_sst_method=mysqldump
wsrep_sst_method=mariabackup

# Address on THIS node to receive SST at. DON'T SET IT TO DONOR ADDRESS!!!
# (SST method dependent. Defaults to the first IP of the first interface)
#wsrep_sst_receive_address=

# SST authentication string. This will be used to send SST to joining nodes.
# Depends on SST method. For mysqldump method it is root:<root password>
# IMPORTANT: The user/password in wsrep_sst_auth must match
# user/password in [xtrabackup]


# Desired SST donor name.
#wsrep_sst_donor=

# Protocol version to use
# wsrep_protocol_version=

# log conflicts
wsrep_log_conflicts=1

[MYSQL]
socket=/var/lib/mysql/mysql.sock
# default_character_set = utf8
[client]
socket=/var/lib/mysql/mysql.sock
# default_character_set = utf8

[mysqldump]
max_allowed_packet = 512M
# default_character_set = utf8



# IMPORTANT: The user/password in wsrep_sst_auth must match
# user/password in [xtrabackup]
[xtrabackup]
databases-exclude=lost+found
ssl_mode=DISABLED




[MYSQLD_SAFE]
# log_error = /var/log/mysqld.log
basedir=/usr/
# datadir = /var/lib/mysql

!include /etc/my.cnf.d/secrets-backup.cnf


[root@galera-mysql2 ~]# cat /etc/my.cnf.d/secrets-backup.cnf
# Security credentials for backup.
[mysqldump]
user=backupuser
password=eZJ8Av8ryRWl9h0B

[xtrabackup]
user=backupuser
password=eZJ8Av8ryRWl9h0B

[mysqld]
wsrep_sst_auth=backupuser:eZJ8Av8ryRWl9h0B