Why Include `localhost` When Using Wildcards in MySQL User Hosts?

Using Wildcards for MySQL User Hosts: Understanding the Need for localhost

In database administration, granting access to users often involves specifying a hostname to limit their connections. When creating MySQL users, a common practice is to use the wildcard character (%) as the host to grant access from any machine. However, some administrators also specify localhost explicitly when using the wildcard.

One might wonder why this additional step is necessary, given that the wildcard should cover all hosts, including localhost. The answer lies in the unique nature of hostname handling in MySQL.

localhost Connection in MySQL

In MySQL, localhost refers specifically to connections made over a UNIX socket or named pipe. These connections provide a direct communication channel between the client and server, without the need for network protocols like TCP/IP. By specifying localhost as a host, you explicitly grant access to this special connection method.

Wildcard Behavior

The wildcard character (%) in a MySQL host specification matches any host, except for localhost. This behavior ensures that users with access to the wildcard can only connect from non-localhost machines. To cater to localhost connections, it is necessary to explicitly include it in the host list.

Conclusion

Therefore, when creating MySQL users and granting them access from "everywhere," it is recommended to include both the wildcard (%) and localhost explicitly. This approach ensures that users can connect from all machines, including localhost, where a special connection method is used.

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