What package is essential for installing MySQL on a Zabbix server?

The choice of "zabbix-server-mysql" is correct because this package specifically includes the necessary components and configurations required for Zabbix to integrate with a MySQL database. When setting up a Zabbix server, it is essential to have this package because it provides the backend capabilities for data storage and retrieval which Zabbix requires to function properly.

In contrast, other packages listed serve different purposes. The "mysql-server" package is a fundamental installation for MySQL itself, providing the server component, but it does not include the Zabbix-specific integrations or configurations that "zabbix-server-mysql" offers. The "zabbix-agent-mysql" is not a standard package related to the Zabbix server setup; rather, it pertains to the Zabbix agent that collects metrics from the monitored hosts. Lastly, the "mysql-client" package is used for interacting with a MySQL database from the command line but does not have relevance to the server setup or Zabbix's requirements for MySQL integration.

Thus, selecting "zabbix-server-mysql" ensures that the Zabbix server operates efficiently with a MySQL database as its backend.