Fatal Error: Can't Open and Lock Privilege Tables: Table 'mysql.host' Doesn't Exist

When MySQL cannot find the mysql.host table, a crucial component for managing user privileges, this error occurs. It often signifies a missing or corrupt MySQL installation, affecting database access and security. This guide covers how to resolve the issue.

Understanding the Error

This error suggests MySQL's system tables, essential for operation, are inaccessible or absent. These tables store user privileges, crucial for secure database operations. Their absence can halt MySQL functionality.

Verifying MySQL Installation

Ensure MySQL is correctly installed. Use your system's package manager to check installation integrity. For example, on Debian-based systems:

sudo dpkg -l | grep mysql

Locating the Data Directory

Find MySQL's data directory, where system tables reside. The default location varies by installation method and operating system. Locate it in the MySQL configuration file (typically my.cnf or my.ini).

grep 'datadir' /etc/mysql/my.cnf

Checking for System Tables

Inspect the data directory for the presence of system tables. List files in the MySQL data directory:

ls /var/lib/mysql/mysql

If host.frm, host.MYD, and host.MYI are missing, system tables need restoration.

Restoring System Tables

Recreate missing system tables using the mysql_install_db tool. This creates default system tables without affecting existing databases.

mysql_install_db --user=mysql --ldata=/var/lib/mysql

Replace /var/lib/mysql with your actual data directory path.

Repairing Corrupt Tables

If system tables exist but are corrupt, repair them using the mysqlcheck tool.

mysqlcheck --repair --all-databases

Reinitializing Permissions

Reset permissions to ensure system table integrity. Start MySQL with skip-grant-tables:

mysqld_safe --skip-grant-tables &

Then, reset permissions:

FLUSH PRIVILEGES;

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