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How to Move the MySQL Data Directory to a New Location on Ubuntu 25.04

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By default, MySQL stores all its data in /var/lib/mysql. This tutorial explains how to safely move the MySQL data directory to a new location (e.g., another disk or partition) on Ubuntu 25.04.

🔧 Step 1: Stop the MySQL Service

Before making any changes, stop the MySQL service:

sudo systemctl stop mysql

🔧 Step 2: Move the Existing Data Directory

Choose your new location, for example /mnt/data/mysql, and move the current data:

sudo mv /var/lib/mysql /mnt/data/mysql

> This moves all database files including system schemas like mysql and performance_schema.

🔧 Step 3: Set Correct Permissions

Ensure MySQL can access the new directory:

sudo chown -R mysql:mysql /mnt/data/mysql

🔧 Step 4: Update MySQL Configuration

Edit the MySQL configuration file:

sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

Find the line:

datadir = /var/lib/mysql

Change it to:

datadir = /mnt/data/mysql

Save and exit.

🔧 Step 5: (If AppArmor is Enabled) Add Access Rules

AppArmor may block MySQL from accessing the new path.

Edit AppArmor profile for MySQL:

sudo nano /etc/apparmor.d/usr.sbin.mysqld

Add these lines before the closing }:

/mnt/data/mysql/ r,
/mnt/data/mysql/** rwk,

Then reload AppArmor:

sudo apparmor_parser -r /etc/apparmor.d/usr.sbin.mysqld

🔧 Step 6: Fix MySQL Socket Directory (Optional)

If needed, recreate the MySQL socket directory:

sudo mkdir -p /var/run/mysqld
sudo chown mysql:mysql /var/run/mysqld

🔧 Step 7: Restart MySQL

sudo systemctl start mysql

✅ Step 8: Verify the New Data Directory

Check that MySQL is using the new path:

mysql -u root -p -e "SHOW VARIABLES LIKE 'datadir';"

You should see:

+---------------+------------------+
| Variable_name | Value            |
+---------------+------------------+
| datadir       | /mnt/data/mysql/ |
+---------------+------------------+

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