MariaDB/MySQL

MariaDB is an open source fork of MySQL. There are some differences but most are internal, for users the commands and SQL syntax is exactly the same.

phpMyAdmin is a web based GUI for the maintenance of MariaDB and MySQL servers.

Performance related queries

show status like 'Qcache_total_blocks'

Fragmentation of the query cache (lower is better)

flush query cache

Flush the query cache to fix the fragmentation (check if cache sizes need to be changed too)

User management

alter user username@host identified by 'password'

Change a users password

drop user username@host

Delete a user

grans all privileges on *.* to 'user'@'host';

Grant all privileges to all database to a user

Move users from one server to another

Starting on the source server execute this script

PASSWORD=$1
mysql -B -N -uroot -p${PASSWORD} -e "SELECT CONCAT('\'', user,'\'@\'', host, '\'') FROM user WHERE user IN ('username1', 'username2', 'username3')" > users.txt
while read line
 do
  mysql -B -N -uroot -p${PASSWORD} -e "SHOW GRANTS FOR $line"
 done < users.txt > users.sql
sed -i 's/$/;/' users.sql

Move the file to the other server and there do:

mysql -u root -p < users.sql

Set up replication

With replication all transactions on the master database server are immediately replicated to the slave database server. So you create a hot copy of the database that can be used in case of a failure of the master server or to offload the master server by executing retrieval queries on the slave.

The slave server logs into the master and checks if the bin-log position differs, if so all transactions after the last binlog-position are redone on the slave.

This procedure is for a large part based on a tutorial found on howtoforge.com [1]

For multi master replication to 1 slave check this.

On the master

Edit the my.cnf so it has below lines.

The server must be accessible from the slave server and the server-id must be unique in you network

The binlog-do-db specifies for which database the binlog is written, one line per database. If omitted for all databases binlog is written except those specified by binlog-ingnore-db.

#skip-networking
#bind-address            = 127.0.0.1
log-bin = /var/log/mysql/mysql-bin.log
#binlog-do-db=exampledb
binlog-ignore-db       = mysql
binlog-ignore-db       = information_schema
binlog-ignore-db       = performance_schema
binlog-ignore-db       = phpmyadmin
server-id=1

Restart the database server

/etc/init.d/mysql restart

Create a replication user

mysql -uroot -p
mysql> GRANT REPLICATION SLAVE ON *.* TO 'slave_user'@'%' IDENTIFIED BY '<some_password>';
mysql> FLUSH PRIVILEGES;

Make sure nothing is changes in the database during backup

mysql> USE exampledb;
mysql> FLUSH TABLES WITH READ LOCK;

Or, for all databases;

mysql> FLUSH TABLES WITH READ LOCK;
mysql> SET GLOBAL read_only = 1;

Check status;

mysql> SHOW MASTER STATUS;
+---------------+----------+--------------+------------------+
| File          | Position | Binlog_do_db | Binlog_ignore_db |
+---------------+----------+--------------+------------------+
| mysql-bin.006 | 183      |              |                  |
+---------------+----------+--------------+------------------+
1 row in set (0.00 sec)

Dump the database

mysqldump -u root -p<password> --opt exampledb > exampledb.sql

Unlock the tables

mysql -u root -p<password>
mysql> UNLOCK TABLES;
mysql> quit;

Or, for all databases;

mysql> SET GLOBAL read_only = 0;
mysql> UNLOCK TABLES;

On the slave server

Create the slave database

mysql -u root -p<password>

CREATE DATABASE exampledb;
quit;

Load the database dump created on the master

mysql -u root -p<password> exampledb < /path/to/exampledb.sql

Edit the my.cnf so it has these lines

The server-id must be unique in you network

The replicate-do-db specifies for which database the binlog on the master is read, one line per database. If omitted for all databases binlog is read.

server-id=2
replicate-do-db=exampledb

Restart the database server

/etc/init.d/mysql restart

In the following statement the values from SHOW MASTER STATUS above must be used.

mysql -u root -p<password>

STOP SLAVE;
CHANGE MASTER TO MASTER_HOST=<masterIP>, MASTER_USER='slave_user', MASTER_PASSWORD='<password>', MASTER_LOG_FILE='mysql-bin.006', MASTER_LOG_POS=183; 
START SLAVE;
quit;

In case of using GTID for replication

mysql -u root -p<password>

CHANGE MASTER TO master_host= <masterIP>', master_user='<slave_user>', MASTER_PASSWORD='<password>', master_use_gtid=current_pos;

SELECT @@GLOBAL.gtid_slave_pos;

Show current GTID position

SET GLOBAL gtid_slave_pos = ""

Reset counter, slave databases must be in sync with the master.

Add a database to replication

Everything must be working fine and log positions up to date. On the slave Read_Master_Log_Pos is the same as the Exec_Master_Log_Pos and the Read_Master_Log_Pos is the same as the masters Position (in show master status).

Then you can do:

• Slave: Add database to my.cnf (replicate-do-db=<dbname>)
• Slave: stop slave;
• Master: flush tables with read lock;
• Master: dump database
• Master: unlock tables
• Slave: Load the database dump
• Slave: Restart the database server

Then check the slave status show slave status \G

Repair replication

On the slave server

Stop replication processes

mysql -u root -p
mysql> stop slave;

On the master server

Dump the replicated databases including the replication data. mysqldump --databases <db1> <db2> --master-data=1 > ../mysql_dump_$(hostname)_$(date +%Y-%m-%d_%H-%M).sql.dump

On the slave server

Import the databases

mysql -uroot -p < <dumpfile>

Restart the slave processes and check the slave status.

When needed update the slave log-file and position as in the masters show slave status

mysql> CHANGE MASTER TO MASTER_LOG_FILE='<filename>', MASTER_LOG_POS=<postition>; 

Then:

mysql> start slave;
mysql> show slave status \G

This should not show any errors

Populate and update timezone information

Timezone information is required to use functions like CONVERT_TZ. The mysql.time_zone table need to be populated and maintained when the data changes.

On a synology server following command takes care of this:

/volume1/@appstore/MariaDB10/usr/local/mariadb10/bin/mysql_tzinfo_to_sql /usr/share/zoneinfo |mysql -uroot -p mysql