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359 lines
12 KiB
Markdown
How to Configure MariaDB Replication on CentOS Linux
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Its a process of creating duplicate versions of a the DB. Replication process is not only copies a database, but also synchronizes changes from master to one of the slaves. But this is does not means that slave databases are identical copy of the master, because replication can be configured that only a schema of tables or columns or rows will be replicated, i.e. a partial replication. The replication ensures that those specific configured objects are kept in sync between the different databases.
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### Mariadb Replication Concepts ###
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**Backups** : Replication can be used for DB backups. For example, you have master -> slave replication. If master is lost (hdd fails, for example) you can restore your db from master.
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**Scaling** : You can use master -> slave replication for scaling solution. For example, if you have a few big and have SQL query, using replcation you can separate this queries for each replcations nodes. Write SQL should be performed only on master, for read-only queries slave server can be used.
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**Spreading solution** : You can use replication for distribution. For example, you can distribute different sales data to different databases.
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**Failover solution** : For example you have, master -> slave(1) -> slave(2) -> slave(3) replication. You can write script for master monitoring , if master fails, script can quickly change slave(1) new for master master -> slave(1) -> slave(2) and your application will continue working whit out downtime
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### Simple diagrammatic demonstration of replication ###
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Before you start good know what is **binary log** and Ibdata1. The binary log contains a record about all changes in the db, data and structure, as well as how long each statement took to execute. Bin log consists set log files and an index. Its means that main SQL statements such as CREATE, ALTER, INSERT, UPDATE and DELETE will be putted to this log, statements, such as SELECT will not be logged. These info can be logged to general query.log file. In simple **Ibdata1** is a file which contains all tables and all info about db.
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### Master server configuration ###
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Good to have server updated
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sudo yum install update -y && sudo yum install upgrade -y
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We are working on centos 7 server
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sudo cat /etc/redhat-release
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CentOS Linux release 7.0.1406 (Core)
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Install MariaDB
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sudo yum install mariadb-server -y
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Start MariaDB and enable it to start on boot of the server
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sudo systemctl start mariadb.service
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sudo systemctl enable mariadb.service
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Output:
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ln -s '/usr/lib/systemd/system/mariadb.service' '/etc/systemd/system/multi-user.target.wants/mariadb.service'
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Check MariaDB status
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sudo service mariadb status
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or use
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sudo systemctl is-active mariadb.service
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Output:
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Redirecting to /bin/systemctl status mariadb.service
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mariadb.service - MariaDB database server
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Loaded: loaded (/usr/lib/systemd/system/mariadb.service; enabled)
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Set MariaDB password
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mysql -u root
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mysql> use mysql;
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mysql> update user set password=PASSWORD("SOME_ROOT_PASSWORD") where User='root';
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mysql> flush privileges;
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mysql> exit
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SOME_ROOT_PASSWORD - your root password. I my case I'ill use "q" - password, then try to login:
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sudo mysql -u root -pSOME_ROOT_PASSWORD
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Output:
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Welcome to the MariaDB monitor. Commands end with ; or \g.
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Your MariaDB connection id is 5
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Server version: 5.5.41-MariaDB MariaDB Server
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Copyright (c) 2000, 2014, Oracle, MariaDB Corporation Ab and others.
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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
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Lets create database with table with some data
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Create database/schema
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sudo mysql -u root -pSOME_ROOT_PASSWORD
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mysql> create database test_repl;
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Where:
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test_repl - Name of shcema which will be replicated
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Output:
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Query OK, 1 row affected (0.00 sec)
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Create Persons table
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mysql> use test_repl;
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CREATE TABLE Persons (
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PersonID int,
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LastName varchar(255),
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FirstName varchar(255),
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Address varchar(255),
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City varchar(255)
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);
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Output:
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mysql> MariaDB [test_repl]> CREATE TABLE Persons (
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-> PersonID int,
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-> LastName varchar(255),
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-> FirstName varchar(255),
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-> Address varchar(255),
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-> City varchar(255)
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-> );
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Query OK, 0 rows affected (0.01 sec)
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Insert some data
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mysql> INSERT INTO Persons VALUES (1, "LastName1", "FirstName1", "Address1", "City1");
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mysql> INSERT INTO Persons VALUES (2, "LastName2", "FirstName2", "Address2", "City2");
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mysql> INSERT INTO Persons VALUES (3, "LastName3", "FirstName3", "Address3", "City3");
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mysql> INSERT INTO Persons VALUES (4, "LastName4", "FirstName4", "Address4", "City4");
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mysql> INSERT INTO Persons VALUES (5, "LastName5", "FirstName5", "Address5", "City5");
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Output:
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Query OK, 5 row affected (0.00 sec)
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Check data
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mysql> select * from Persons;
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Output:
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+----------+-----------+------------+----------+-------+
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| PersonID | LastName | FirstName | Address | City |
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+----------+-----------+------------+----------+-------+
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| 1 | LastName1 | FirstName1 | Address1 | City1 |
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| 1 | LastName1 | FirstName1 | Address1 | City1 |
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| 2 | LastName2 | FirstName2 | Address2 | City2 |
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| 3 | LastName3 | FirstName3 | Address3 | City3 |
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| 4 | LastName4 | FirstName4 | Address4 | City4 |
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| 5 | LastName5 | FirstName5 | Address5 | City5 |
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+----------+-----------+------------+----------+-------+
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### Configure MariaDB for replication ###
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You'll need to edit the my.cnf file on the Master server to enable binary logging and set the server's id. I will use vi text editor, but use can use any suitable for your such as nano, joe etc.
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sudo vi /etc/my.cnf
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and put to config in [mysqld] section such lines.
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log-basename=master
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log-bin
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binlog-format=row
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server_id=1
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Output:
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Then restart MariaDB:
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sudo service mariadb restart
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Login to MariaDB and check binary logs:
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sudo mysql -u root -pq test_repl
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mysql> SHOW MASTER STATUS;
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Output:
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+--------------------+----------+--------------+------------------+
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| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
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+--------------------+----------+--------------+------------------+
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| mariadb-bin.000002 | 3913 | | |
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+--------------------+----------+--------------+------------------+
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**Remember** : "File" and "Position" values. YOU WILL NEED THIS VALUE AT SLAVE SERVER
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Create user for replication
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mysql> GRANT REPLICATION SLAVE ON *.* TO replication_user IDENTIFIED BY 'bigs3cret' WITH GRANT OPTION;
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mysql> flush privileges;
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Output:
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Query OK, 0 rows affected (0.00 sec)
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Query OK, 0 rows affected (0.00 sec)
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Check user in db
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mysql> select * from mysql.user WHERE user="replication_user"\G;
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Output:
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mysql> select * from mysql.user WHERE user="replication_user"\G;
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*************************** 1. row ***************************
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Host: %
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User: replication_user
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Password: *2AF30E7AEE9BF3AF584FB19653881D2D072FA49C
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Select_priv: N
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.....
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Create DB dump (snapshot of all data which will be replicated) form master
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mysqldump -uroot -pSOME_ROOT_PASSWORD test_repl > full-dump.sql
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Where:
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SOME_ROOT_PASSWORD - password for root user that you have setup
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test_repl - name of the data base which will be replicated;
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You need to recover mysql dump (full-dump.sql) at slave server. Its needed for replication.
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### Slave server configuration ###
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All this commands you need to perform at slave server
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Lets assume that we have fresh/updated CentOS 7.x server with latest mariaDB server and you can login as root to maria DB server (this was descripbed in first part of the article)
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Login to Maria DB console and create DB
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mysql -u root -pSOME_ROOT_PASSWORD;
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mysql> create database test_repl;
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mysql> exit;
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Recover data from master at slave server
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mysql -u root -pSOME_ROOT_PASSWORD test_repl < full-dump.sql
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Where:
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full-dump.sql - its DB Dump that you have create at test server.
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Login to Maria DB and setup replication
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mysql> CHANGE MASTER TO
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MASTER_HOST='82.196.5.39',
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MASTER_USER='replication_user',
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MASTER_PASSWORD='bigs3cret',
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MASTER_PORT=3306,
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MASTER_LOG_FILE='mariadb-bin.000002',
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MASTER_LOG_POS=3913,
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MASTER_CONNECT_RETRY=10;
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Where:
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MASTER_HOST - IP of the master server.
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MASTER_USER - replication user at master server
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MASTER_PASSWORD - replication user password
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MASTER_PORT - mysql port at master
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MASTER_LOG_FILE - bin-log file name form master
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MASTER_LOG_POS - bin-log position file at master
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Start slave mode
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mysql> slave start;
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Output:
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Query OK, 0 rows affected (0.00 sec)
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Check slave status
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mysql> show slave status\G;
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Output:
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*************************** 1. row ***************************
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Slave_IO_State: Waiting for master to send event
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Master_Host: 82.196.5.39
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Master_User: replication_user
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Master_Port: 3306
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Connect_Retry: 10
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Master_Log_File: mariadb-bin.000002
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Read_Master_Log_Pos: 4175
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Relay_Log_File: mariadb-relay-bin.000002
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Relay_Log_Pos: 793
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Relay_Master_Log_File: mariadb-bin.000002
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Slave_IO_Running: Yes
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Slave_SQL_Running: Yes
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Replicate_Do_DB:
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Replicate_Ignore_DB:
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Replicate_Do_Table:
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Replicate_Ignore_Table:
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Replicate_Wild_Do_Table:
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Replicate_Wild_Ignore_Table:
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Last_Errno: 0
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Last_Error:
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Skip_Counter: 0
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Exec_Master_Log_Pos: 4175
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Relay_Log_Space: 1089
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Until_Condition: None
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Until_Log_File:
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Until_Log_Pos: 0
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Master_SSL_Allowed: No
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Master_SSL_CA_File:
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Master_SSL_CA_Path:
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Master_SSL_Cert:
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Master_SSL_Cipher:
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Master_SSL_Key:
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Seconds_Behind_Master: 0
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Master_SSL_Verify_Server_Cert: No
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Last_IO_Errno: 0
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Last_IO_Error:
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Last_SQL_Errno: 0
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Last_SQL_Error:
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Replicate_Ignore_Server_Ids:
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Master_Server_Id: 1
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1 row in set (0.00 sec)
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At this step all shoul be ok, and not erros should be here.
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### Test the replication ###
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At MAIN/MASTER server add some entities to DB
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mysql -u root -pSOME_ROOT_PASSWORD test_repl
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mysql> INSERT INTO Persons VALUES (6, "LastName6", "FirstName6", "Address6", "City6");
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mysql> INSERT INTO Persons VALUES (7, "LastName7", "FirstName7", "Address7", "City7");
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mysql> INSERT INTO Persons VALUES (8, "LastName8", "FirstName8", "Address8", "City8");
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Then go to the SLAVE server and check replicated data
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mysql -u root -pSOME_ROOT_PASSWORD test_repl
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mysql> select * from Persons;
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+----------+-----------+------------+----------+-------+
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| PersonID | LastName | FirstName | Address | City |
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+----------+-----------+------------+----------+-------+
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...................
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| 6 | LastName6 | FirstName6 | Address6 | City6 |
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| 7 | LastName7 | FirstName7 | Address7 | City7 |
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| 8 | LastName8 | FirstName8 | Address8 | City8 |
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+----------+-----------+------------+----------+-------+
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You can see the data is replicated to slave server. Its mean that replication is working. Hope you enjoyed the article. Let us know if you have any questions.
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--------------------------------------------------------------------------------
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via: http://linoxide.com/how-tos/configure-mariadb-replication-centos-linux/
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作者：[Bobbin Zachariah][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://linoxide.com/author/bobbin/ |