The next few sections contain information about mysqld options and server variables that are used in replication and for controlling the binary log. Options and variables for use on replication masters and replication slaves are covered separately, as are options and variables relating to binary logging. A set of quick-reference tables providing basic information about these options and variables is also included (in the next section following this one).
Of particular importance is the
--server-id option.
| Command-Line Format | --server-id=# | ||
| Option-File Format | server-id | ||
| Option Sets Variable | Yes, server_id | ||
| Variable Name | server_id | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 0 | ||
| Range | 0-4294967295 | ||
This option is common to both master and slave replication servers, and is used in replication to enable master and slave servers to identify themselves uniquely. For additional information, see Section 17.1.3.2, “Replication Master Options and Variables”, and Section 17.1.3.3, “Replication Slave Options and Variables”.
On the master and each slave, you must use the
--server-id option to establish a
unique replication ID in the range from 1 to
232 – 1. “Unique”,
means that each ID must be different from every other ID in use by
any other replication master or slave. Example:
server-id=3.
If you omit --server-id, the default
ID is 0, in which case a master refuses connections from all slaves,
and a slave refuses to connect to a master. For more information,
see Section 17.1.1.2, “Setting the Replication Slave Configuration”.