Changing the MariaDB 5.5 Data Directory: Configuration and Path Management

In MariaDB (and its close relative, MySQL), the datadir (data directory) is a crucial location on your system where MariaDB stores all its database files. These files include information about your databases, tables, indexes, and other essential data.

Why change datadir?

There are several reasons why you might want to change the data directory:

• Separate data from system files: By placing the data on a dedicated partition or drive, you can improve performance and simplify system administration tasks like backups or upgrades.
• Storage limitations: If your system drive is running low on space, moving the data directory to a larger drive can be helpful.
• Security considerations: In specific scenarios, isolating data from application files can enhance security.

Steps to change datadir:

2. Find the current datadir: Locate the existing data directory's path. This is usually /var/lib/mysql on Linux systems. You can verify this by using the following command:

   mysqladmin --verbose | grep datadir
   

   This command outputs various configuration details, including the datadir line.

3. Copy the data directory: Create a new directory where you want to store the MariaDB data from now on. Then, use the cp -r command (or its equivalent on your system) to copy the entire existing data directory to the new location. For example:

   sudo cp -rp /var/lib/mysql /new/data/directory
   

   The -r flag ensures that the entire directory structure is copied recursively, preserving all files and subdirectories.

Additional considerations:

• SELinux (Linux): If you're using a Linux distribution with Security-Enhanced Linux (SELinux) enabled, you might need to adjust the SELinux context of the new data directory to allow MariaDB to access it. Refer to your distribution's documentation for specific steps.
• Permissions: Double-check that MariaDB has the necessary permissions to read, write, and modify files within the new data directory.

sudo service mysqld stop

Finding current datadir:

mysqladmin --verbose | grep datadir

This will output something like:

datadir  /var/lib/mysql

Copying the data directory (assuming new location is /new/data/dir):

sudo cp -rp /var/lib/mysql /new/data/dir

Editing the configuration file (assuming file is /etc/my.cnf):

Open /etc/my.cnf with a text editor with root privileges.

Updating the datadir setting:

Find the [mysqld] section and modify the datadir line to:

[mysqld]
datadir=/new/data/dir

Restarting MariaDB:

sudo service mysqld start

Note: These are examples specific to Linux systems. The commands for stopping and starting MariaDB might differ on Windows or other operating systems. Refer to your system's documentation for exact commands.

• Permissions: You might need to adjust ownership and permissions for the new data directory using commands like sudo chown and sudo chmod. Consult your system's documentation for details.
• SELinux: If using SELinux, adjust the context of the new data directory as needed.

Instead of using service mysqld stop and service mysqld start, you can directly manage the MariaDB server process with mysqld_safe. This method offers more control over startup options:

sudo mysqld_safe --socket=/path/to/socket --datadir=/new/data/dir &

Replace /path/to/socket with the desired socket file path (usually /var/run/mysqld/mysqld.sock) and /new/data/dir with your new data directory. The & at the end runs the command in the background.

Symbolic Link (Linux):

While not recommended for production environments due to potential performance overhead, you can create a symbolic link from the existing data directory to the new location. This approach avoids copying the entire directory structure:

2. Create a symbolic link:

   sudo ln -s /new/data/dir /var/lib/mysql
   

Important Considerations:

• Symbolic Link Issues: Using a symbolic link can introduce performance overhead and potential issues during upgrades or data directory repairs. It's generally not recommended for critical databases.
• Permissions: Ensure the user running MariaDB has permissions to access both the original and new data directory locations.

Remember:

• Test the changes thoroughly in a non-production environment before implementing them on your main database server.