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MySQL - how to set up complete replication on your current MySQL server
Below is a quick description of how to set up complete replication on your current MySQL server. It assumes you want to
replicate all your databases and have not configured replication before. You will need to shutdown your master server
briefly to complete the steops outlined below.
Make sure you have a recent version of MySQL installed on the master and slave(s). Use Version 3.23.29 or higher. Previous
releases used a different binary log format and had bugs which have been fixed in newer releases. Please, do not report bugs
until you have verified that the problem is present in the latest release.
Set up special a replication user on the master with the FILE privilege and permission to connect from all the slaves. If
the user is only doing replication (which is recommended), you don't need to grant any additional privileges. For example,
to create a user named repl which can access your master from any host, you might use this command:
GRANT FILE ON *.* TO repl@"%" IDENTIFIED BY '';
Shut down MySQL on the master.
mysqladmin -u root -p<password> shutdown
Snapshot all the data on your master server. The easiest way to do this (on Unix) is to simply use tar to produce an archvie
of your entrie data directory. The exact data directory location depends on your installation.
tar -cvf /tmp/mysql-snapshot.tar /path/to/data-dir
Windows users can use WinZip or similar software to create an archive of the data directory.
In my.cnf on the master add log-bin and server-id=unique number to the [mysqld] section and restart it. It is very important
that the id of the slave is different from the id of the master. Think of server-id as something similar to the IP address -
it uniquely identifies the server instance in the comminity of replication partners.
[mysqld]
log-bin
server-id=1
Restart MySQL on the master.
Add the following to my.cnf on the slave(s):
master-host=<hostname of the master>
master-user=<replication user name>
master-password=<replication user password>
master-port=<TCP/IP port for master>
server-id=<some unique number between 2 and 2^32-1>
replacing the values in <> with what is relevant to your system. server-id must be different for each server participating
in replication. If you don't specify a server-id, it will be set to 1 if you have not defined master-host, else it will be
set to 2. Note that in the case of server-id omission the master will refuse connections from all slaves, and the slave will
refuse to connect to a master. Thus, omitting server-id is only good for backup with a binary log.
Copy the snapshot data into your data directory on your slave(s). Make sure that the privileges on the files and directories
are correct. The user which MySQL runs as needs to be able to read and write to them, just as on the master.
Restart the slave(s).
After you have done the above, the slave(s) should connect to the master and catch up on any updates which happened since
the snapshot was taken.
If you have forgotten to set server-id for the slave you will get the following error in the error log file:
Warning: one should set server_id to a non-0 value if master_host is set.
The server will not act as a slave.
If you have forgot to do this for the master, the slaves will not be able to connect to the master.
If a slave is not able to replicate for any reason, you will find error messages in the error log on the slave.
Once a slave is replicating, you will find a file called master.info in the same directory as your error log. The
master.info file is used by the slave to keep track of how much of the master's binary log is has processed. Do not remove
or edit the file, unless you really know what you are doing. Even in that case, it is preferred that you use CHANGE MASTER
TO command.
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