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README.md
206
README.md
@ -7,18 +7,220 @@ Setup a mariadb slave server with automysqlbackup
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## Parameters
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### SERVER_ID
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This is used to customize slave server ID. The default value is 33. You should use an unique ID for each server.
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### READONLY
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When set to **1**, the slave server is set as readonly. This is the default. If you set this variable to something different, the database will be read/write.
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### REPLICATE_DO_DB
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This is used to specify a single database to backup. It is generally advised to set this variable to the database name you want to backup.
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## How to setup a mysql slave for backup
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### Configure the master node
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Examine all mariadb config files, they're usually located in **/etc/mysql/**. You must have these instructions:
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```
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[mysqld]
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server_id = 1
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log_bin
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log-bin = binlog
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max-binlog-size = 500M
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binlog-do-db = my-db-name
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bind-address = 0.0.0.0
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```
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$ docker exec some-mariadb sh -c 'exec mysqldump --all-databases -uroot -p"$MYSQL_ROOT_PASSWORD"' > /some/path/on/your/host/all-databases.sql
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You must have an unique server_id and binlog enabled (the max-binlog-size is purely an example). The bind-address is here to make sure your server is reachable from the backup node. Maybe you can consider a firewall rule if your db shouldn't be reached from outside. The binlog-do-db is used to specify which database you want to be used with binlog; you can have multiple binlog-do-db lines if you need to replicate more than one db.
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After these modifications, restart mariadb.
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2019-11-24 10:57:24 0 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--log-basename=#' or '--relay-log=mysqld-relay-bin' to avoid this problem.
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### Create a replication user
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Execute this statement on the master node:
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```
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grant replication slave on *.* to repluser@backupslave.host identified by 'aRandomPassword'; flush privileges;
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```
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Replace **repluser**, **backupslave.host**, **aRandomPassword** with something more meaningful. Please take note that **in replication you cannot use a password longer than 32 characters**.
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### Start the slave server
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We use docker-compose here, but you can do the same with plain docker. Here's a sample **docker-compose.yaml** file:
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```
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version: "3"
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services:
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backup-slave:
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image: docker.asperti.com/paspo/mariadb-backup-slave
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restart: always
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volumes:
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- "./mysql/:/var/lib/mysql"
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- "./backup/:/var/lib/automysqlbackup"
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environment:
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- MYSQL_ROOT_PASSWORD=aSecurePassword
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- SERVER_ID=3
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- READONLY=0
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- REPLICATE_DO_DB=aWordpressDatabase
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```
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Start the container:
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```
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docker-compose up -d
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```
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Create the database:
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```
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docker exec my-container sh -c 'echo "create database aWordpressDatabase;" | exec mysql -uroot -p"$MYSQL_ROOT_PASSWORD"'
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```
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### Freeze the master
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To obtain a consistant slave, you first have to freeze the master, and then transfer the data.
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Execute this on the master:
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```
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FLUSH TABLES WITH READ LOCK;
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show master status;
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```
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***Keep this session running!!!*** If you close it, it will release the lock.
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Take note of file and position, we'll need these informations later.
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### Import initial data
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We have two ways to copy the data from the master to the slave: we'll call these "live" and "classic".
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The classic way is the usual mysqldump + file transfer + import.
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The live way is dump + import at the same time, without an intermediate file.
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The live way is preferred when you have small databases (less than 5Gb) and a good bandwidth (100+ Mbit) available between the master and the slave.
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The classic way is preferred when you have a big database because it locks the database for less time.
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### Import initial data (live version)
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Now, we need to import the backup from the master, so as we started the slave as readwrite, we can now do this on the slave:
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```
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docker exec my-container sh -c 'mysqldump -C --lock-tables=false --quick -u repluser -h master.host --password="aRandomPassword" aWordpressDatabase | mysql -u root -p"$MYSQL_ROOT_PASSWORD" aWordpressDatabase'
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```
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Replace **my-container**, **repluser**, **master.host**, **aRandomPassword**, **aWordpressDatabase** with the correct values.
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Now that the slave has got some data, we can release the lock in the master:
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```
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UNLOCK TABLES;
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```
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### Import initial data (classic version)
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In the master we run mysqldump in a shell:
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```
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mysqldump -u root -p aWordpressDatabase | gzip > thedump.sql.gz
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```
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When the export is finished, we can let the master resume his work, by issuing this command in the previous mysql session:
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```
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UNLOCK TABLES;
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```
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We can proceed to transfer the dump file to the slave; use the method you prefer.
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On the slave, copy the dump file in the running container, like this:
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```
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docker cp thedump.sql.gz my-container:/thedump.sql.gz
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```
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Then we import it:
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```
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docker exec my-container sh -c 'zcat /thedump.sql.gz | mysql -u root -p"$MYSQL_ROOT_PASSWORD" aWordpressDatabase'
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docker exec my-container sh -c 'rm /thedump.sql.gz'
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```
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Replace **my-container**, **aWordpressDatabase** with the correct values.
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### Start the slave
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Open a mysql console in the slave:
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```
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docker exec -ti my-container sh -c 'mysql -u root -p"$MYSQL_ROOT_PASSWORD" aWordpressDatabase'
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```
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And configure the replication:
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```
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STOP SLAVE;
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RESET SLAVE;
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CHANGE MASTER TO
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MASTER_HOST='master.host',
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MASTER_USER='repluser',
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MASTER_PASSWORD='aRandomPassword',
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MASTER_PORT=3306,
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MASTER_LOG_FILE='binlog.000007',
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MASTER_LOG_POS=1234567,
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MASTER_HEARTBEAT_PERIOD=60,
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MASTER_CONNECT_RETRY=10;
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START SLAVE;
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```
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### Check replication status
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```
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docker exec -ti my-container sh -c 'mysql -u root -p"$MYSQL_ROOT_PASSWORD" aWordpressDatabase -e "SHOW SLAVE STATUS\G;"'
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```
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Example output:
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```
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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: master.host
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Master_User: repluser
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Master_Port: 3306
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Connect_Retry: 10
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Master_Log_File: binlog.000008
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Read_Master_Log_Pos: 12392188
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Relay_Log_File: backup-slave-relay-bin.000002
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Relay_Log_Pos: 51478388
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Relay_Master_Log_File: binlog.000007
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Slave_IO_Running: Yes
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Slave_SQL_Running: Yes
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Replicate_Do_DB: aWordpressDatabase
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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: 252550180
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Relay_Log_Space: 116716314
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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: 31939
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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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Master_SSL_Crl:
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Master_SSL_Crlpath:
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Using_Gtid: No
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Gtid_IO_Pos:
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Replicate_Do_Domain_Ids:
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Replicate_Ignore_Domain_Ids:
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Parallel_Mode: conservative
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1 row in set (0.00 sec)
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```
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In a normal condition, **Slave_IO_Running** and **Slave_SQL_Running** should be **Yes**: this means that the communication between master and slave is ok and no sync error has occourred. **Seconds_Behind_Master** is usually 0, except wen the communication has just been established and the slave has to catch up with the master. This situation usually resolves in some time.
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### Make the slave read-only
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For a safety measure, we're enabling read-only mode for the slave: we don't have to run any query on this host, we're just using it for scheduled backups.
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Reopen **docker-compose.yaml**, change **READONLY=0** to **READONLY=1** and restart the container:
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```
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docker-compose up -d
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```
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## How to use different mariadb version
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The default is mariadb 10.3.
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If you want, you can use mariadb 10.2 or 10.1 by changing this line in **docker-compose.yaml**:
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```
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image: docker.asperti.com/paspo/mariadb-backup-slave:maria-10.1
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```
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