I was recently working on an instance of MariaDB where I loaded almost 200GB of data. My /var folder filled up almost to 90% and I got all sorts of warning logs about size limitations, etc. Before it turned into bigger issue, I decided to take proactive approach and move my data to another location.
Useful command to check the size
$ sudo du -sch *
Verify current data directory location
$ mysql -u root -p
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 4
Server version: 10.1.33-MariaDB MariaDB Server
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> select @@datadir;
+--------------------------+
| @@datadir |
+--------------------------+
| /var/lib/mysql/ |
+--------------------------+
1 row in set (0.00 sec)
MariaDB [(none)]> exit
Bye
Stop running mariadb instance
$ sudo systemctl stop mariadb
$ sudo systemctl status mariadb
Double check if instance is running (Force kill any rogue mysql processes) and check if port 3306 is still occupied
$ ps -elf|grep mysql
$ netstat -apn | grep 3306
Move data to new location and back up old instance
$ sudo rsync -av /var/lib/mysql /mnt/big_data
$ sudo mv /var/lib/mysql /var/lib/mysql.bak
Edit configuration files to change the defaults.
"/etc/my.cnf"
[mysqld]
datadir=/mnt/big_data/mysql/
socket=/mnt/big_data/mysql/mysql.sock
"/etc/my.cnf.d/client.cnf"
[client]
port=3306
socket=/mnt/big_data/mysql/mysql.sock
I also had to chmod new directory, otherwise mariadb was failing since it could not write to the new location.
Start it back up and make sure that new directory is in use
$ sudo systemctl start mariadb
$ sudo systemctl status mariadb
$ mysql -u root -p
MariaDB [(none)]> select @@datadir;
+--------------------------+
| @@datadir |
+--------------------------+
| /mnt/big_data/mysql/ |
+--------------------------+
1 row in set (0.00 sec)