Difference between [mysql] and [mysqld] in MySQL configuration file

Question

There are multiple sections in MySQL configuration file:

• [mysql]
• [mysqld]
• [myisamchk]
• [mysqld_safe]
• [mysqlhotcopy]
• [mysqldump]
• [client]

I found that same variables with different values have been defined under these sections.

• What are the specific purpose behind defining these sections?
• Is it necessary to define all?
• How MySQL interprets these variables?

Answer 1

MySQL calls these section "Groups". The [mysqld] group contains the variables apply to the MySQL Server (the mysqld process). The [mysql] group contains the variables for the client program (mysql).

The [client] option group is read by all client programs (but not by mysqld), so "mysql", "mysqldump" etc...

None of these groups are mandatory but usually we set at least the [mysqld] because it's where we configure the server.

About how MySQL interprets these variables, MySQL Documentation says:

If an option group name is the same as a program name, options in the group apply specifically to that program.

Max