Move MySQL default storage place

The BeagleBone Black has a standard 2 GB built-in flash memory , but that can sometime be pretty close depending on the installed operating system and installed programs .

Moreover, it is quite useful to have certain applications, such as a php- based CMS to run with MySQL database on faster memory such as USB flash or an external USB hard drive .

How to add storage to a BeagleBone Black is described here Enhance Storage on the Beaglebone Black

By default , MySQL stores its databases in Debian in the folder /var/lib/mysql . If you go to the internal memory has no more space and want to move the location to external storage media , which is actually pretty easy.

1. create a folder on the external storage, for example,
   

   mkdir /path-to-mountpoint/mysql/

2. set the necessary permissions for the folder with
   

   chown -R mysql:mysql /path-to-mountpoint/mysql/

   ( chown = change owner and by the -R the permissions are set recursively , ie including folders and subfolders )

3. copy all files from the old directory to the new folder
   

   cp -r /var/lib/mysql/* /path-to-mountpoint/mysql/ 

4. adjust the configuration file of MySQL li>

To customize the configuration file open it in a text editor of your choice - such as nano.
The file is a little more complex , but the important part is this

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

There, the entry "datadir" is adjusted in that way, that it points to the newly created folder.

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /path-to-mountpoint/mysql/
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

Save the file and restart MySQL with service mysql restart and thats it.

Note
After moving the databases to a USB-attached hard disk, it always came to problems and errors in MySQL. Moving to an installed SD card on the other hand runs smoothly.