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Changing ‘cmon’ or ‘root’ Password

For MySQL-based clusters, ClusterControl requires two database users, ‘cmon’ and ‘root’ with full privileges and grant options. Most of the time, ClusterControl will use ‘cmon’ users for monitoring, management, and maintenance operations. However, there are some operations which only the ‘root’ user is capable of performing like granting ‘cmon’ user for the first time after restoration and scaling up a new database node.

In the ClusterControl context, both ‘cmon’ and ‘root’ users are immutable. The password is defined under mysql_password variable for ‘cmon’, while for the MySQL root password should be defined under monitored_mysql_root_password variable. The variable mysql_password exists in every cluster’s CMON configuration file, located under /etc/cmon.d directory. Thus, if you have 5 clusters managed by this ClusterControl instance, you need to update the mysql_password variable for 6 times (1 inside /etc/cmon.cnf + 5 inside /etc/cmon.d/cmon_*.cnf), as shown in the Changing cmon Password section.

Changing cmon Password

Note

Before changing the ‘cmon’ database user password, you must know the MySQL root password for the ClusterControl node and all of the database nodes.

The steps are:

1. Stop ClusterControl Controller (CMON) service:

$ systemctl stop cmon # systemd
$ service cmon stop # sysvinit

2. Update the ‘cmon’ user password on the ClusterControl node. Retrieve the user host information for ‘cmon’ beforehand:

mysql> SELECT user,host FROM mysql.user WHERE user = 'cmon';
+------+------------+
| user | host       |
+------+------------+
| cmon | 10.0.0.156 |
| cmon | 127.0.0.1  |
| cmon | localhost  |
+------+------------+

Then update the ‘cmon’ password for every host accordingly:

mysql> SET PASSWORD FOR `cmon`@`10.0.0.156` = PASSWORD('&5?2+SW9bGq');
mysql> SET PASSWORD FOR `cmon`@`127.0.0.1` = PASSWORD('&5?2+SW9bGq');
mysql> SET PASSWORD FOR `cmon`@`localhost` = PASSWORD('&5?2+SW9bGq');

3. Update the ‘cmon’ user password on all monitored MySQL nodes. Retrieve the user host information for ‘cmon’ beforehand:

mysql> SELECT user,host FROM mysql.user WHERE user = 'cmon';
+------+------------+
| user | host       |
+------+------------+
| cmon | 10.0.0.156 |
| cmon | cc.local   |

When updating the password, run the following statements on the correct node depending on the cluster type:

  • On one of the MySQL node for Galera Cluster.
  • On the master server for MySQL Replication.
  • On the primary node for MySQL Group Replication.
  • On all MySQL API nodes for MySQL Cluster (NDB).
mysql> SET PASSWORD FOR `cmon`@`10.0.0.156` = PASSWORD('&5?2+SW9bGq');
mysql> SET PASSWORD FOR `cmon`@`cc.local` = PASSWORD('&5?2+SW9bGq');

4. Edit the value of mysql_password variables inside all ClusterControl related files:

  • CMON main configuration file: /etc/cmon.cnf under mysql_password variable.
  • Cluster configuration file: /etc/cmon.d/cmon_*.cnf under mysql_password variable.
  • ClusterControl UI configuration file: /var/www/html/clustercontrol/bootstrap.php under DB_PASS constant.

The following output shows the post-edited value when filtering out the password variables:

$ cat /etc/cmon.cnf | grep ^mysql_password
mysql_password='&5?2+SW9bGq'
$ cat /etc/cmon.d/cmon_1.cnf | grep ^mysql_password # Galera Cluster
mysql_password='&5?2+SW9bGq'
$ cat /etc/cmon.d/cmon_2.cnf | grep ^mysql_password # MySQL Replication
mysql_password='&5?2+SW9bGq'
$ cat /var/www/html/clustercontrol/bootstrap.php | grep DB_PASS
define('DB_PASS', '&5?2+SW9bGq');
Note

If you don’t like repetition, you can use Linux replace tool like sed to do the job in one shot.

5. Start ClusterControl Controller (CMON) service:

$ systemctl start cmon # systemd
$ service cmon start # sysvinit

Verify if CMON starts correctly by looking at the /var/log/cmon.log or /var/log/cmon_*.log.

Changing MySQL Root Password of your Database Server/Cluster

ClusterControl requires a working MySQL root password for management, restoration and granting purposes. It is not necessary for MySQL root user to be granted remote access because all operations involving this user will be executed via SSH locally. Use monitored_mysql_root_password value to set the correct password in the CMON configuration file for the respective cluster.

The basic steps involve changing the MySQL root password, update monitored_mysql_root_password variable in the respective CMON configuration file and restart the ClusterControl (CMON) service. For example, suppose we are having 3 MySQL-based clusters managed by a single ClusterControl server (10.0.0.156) and we would like to update the MySQL root password on all clusters, with the following cluster ID and configuration file:

Cluster ID Configuration File
MariaDB Galera Cluster 1 /etc/cmon.d/cmon_1.cnf
MySQL Replication 2 /etc/cmon.d/cmon_2.cnf
MySQL Cluster (NDB) 3 /etc/cmon.d/cmon_3.cnf

1. Update the MySQL root user password on all monitored MySQL nodes. Retrieve the user host information for root beforehand:

mysql> SELECT user,host FROM mysql.user WHERE user = 'root';
+------+------------+
| user | host       |
+------+------------+
| root | localhost  |
| root | ::1        |
| root | 127.0.0.1  |
+------+------------+

When updating the password, run the following statements on the correct node depending on the cluster type:

  • On one of the MySQL node for Galera Cluster.
  • On the master server for MySQL Replication.
  • On the primary node for MySQL Group Replication.
  • On all MySQL API nodes for MySQL Cluster (NDB).
mysql> SET PASSWORD FOR `root`@`localhost` = PASSWORD('&5?2+SW9bGq');
mysql> SET PASSWORD FOR `root`@`::1` = PASSWORD('&5?2+SW9bGq');
mysql> SET PASSWORD FOR `root`@`127.0.0.1` = PASSWORD('&5?2+SW9bGq');

2.Edit the value of monitored_mysql_root_password variable inside the respective CMON configuration for that particular cluster ID. For example, if we changed the root password for cluster ID 2, we would need to update the value inside /etc/cmon.d/cmon_2.cnf accordingly. The following output shows the post-edited value when filtering out the password variables for all clusters (assuming we have changed the MySQL root password on all clusters to ‘&5?2+SW9bGq’):

$ cat /etc/cmon.d/cmon_1.cnf | grep ^monitored_mysql_root_password
monitored_mysql_root_password='&5?2+SW9bGq'
$ cat /etc/cmon.d/cmon_2.cnf | grep ^monitored_mysql_root_password
monitored_mysql_root_password='&5?2+SW9bGq'
$ cat /etc/cmon.d/cmon_3.cnf | grep ^monitored_mysql_root_password
monitored_mysql_root_password='&5?2+SW9bGq

3. Restart ClusterControl Controller (CMON) service to load the changes:

$ systemctl restart cmon # systemd
$ service cmon restart # sysvinit
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