Mysql Database Moving Data Directory to New Location.

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mysql centos linux

How to move an existing data directory in mysql to a new location. We were running out of space and had to move the existing data directory to a new drive. Below are the steps to move the data directory to new location.

Stop mysql using the following command:

sudo service mysqld stop

Copy the existing data directory (default located in /var/lib/mysql) using the following command:

sudo mkdir /db 
sudo cp -R -p /var/lib/mysql /db

Update the mysql configuration file with new path /db/mysql the following command:

sudo vim /etc/my.cnf

Here is how the configuration looks like.

[ahmed@localhost mysql]$ cat /etc/my.cnf 
[mysqld]
datadir=/db/mysql
socket=/db/mysql/mysql.sock
user=mysql
#  Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
[ahmed@localhost mysql]$ 

Look for the entry for datadir, and change the path (which should be /var/lib/mysql) to the new data /db/mysql directory.

In the terminal, enter the command:

sudo vim /etc/rc.d/init.d/mysqld

Look for lines beginning with /var/lib/mysql. Change /var/lib/mysql in the lines with the new path /db/mysql. Save and close the file.

51 get_mysql_option mysqld datadir "/db/mysql"
52 datadir="$result"
53 echo $datadir
54 get_mysql_option mysqld socket "$datadir/mysql.sock"
55 socketfile="$result"
56 get_mysql_option mysqld_safe log-error "/var/log/mysqld.log"
57 errlogfile="$result"
58 get_mysql_option mysqld_safe pid-file "/var/run/mysqld/mysqld.pid"
59 mypidfile="$result"

Move the existing mysql directory

sudo mv /var/lib/mysql /var/lib/mysql_old

Create a symbolic link to the new path.

cd /var/lib
sudo ln -s /db/mysql mysql

Restart mysql with the command:

sudo service mysqld restart

Now login to mysql and you can access the same databases you had before.

Written on February 4, 2016