title: MariaDB failed to start after change of datadir
body: <p>Background Info:</p>
  
  <p>I let the CentOS 7 installer to partition automatically.</p>
  
  <pre><code>Filesystem               Size  Used Avail Use% Mounted on
  /dev/mapper/centos-root   50G   43G  7.9G  85% /
  devtmpfs                  32G     0   32G   0% /dev
  tmpfs                     32G     0   32G   0% /dev/shm
  tmpfs                     32G  9.3M   32G   1% /run
  tmpfs                     32G     0   32G   0% /sys/fs/cgroup
  /dev/sda1                492M  123M  369M  25% /boot
  /dev/mapper/centos-home  476G   54G  422G  12% /home
  tmpfs                    6.3G     0  6.3G   0% /run/user/1000
  tmpfs                    6.3G     0  6.3G   0% /run/user/0
  </code></pre>
  
  <p>But I didn't expect not most of the disk space goes to the / root directory,
  and MariaDB is now 35GB in /var/lib/mysql running out of space soon.</p>
  
  <p>So I changed the datadir, by commands below, but then failed to start</p>
  
  <pre><code>systemctl stop mariadb
  cp -fR /var/lib/mysql /home/
  chown -R mysql:mysql /home/mysql
  </code></pre>
  
  <p>vi /etc/my.cnf.d/server.cnf 
  and added the following line</p>
  
  <pre><code>[mysqld] 
  datadir=/home/mysql
  </code></pre>
  
  <p>systemctl start mariadb</p>
  
  <p>but it failed and compliant about "Can't create test file"</p>
  
  <pre><code>Jul 06 22:32:26 ging2 systemd[1]: Starting MariaDB database server...
  Jul 06 22:32:26 ging2 mysqld[9450]: 2017-07-06 22:32:26 140114825693312 [Note] options --log-slow-admin-statements, --log-queries-not-us...s not set
  Jul 06 22:32:26 ging2 mysqld[9450]: 2017-07-06 22:32:26 140114825693312 [Note] /usr/sbin/mysqld (mysqld 10.2.5-MariaDB) starting as process 9450 ...
  Jul 06 22:32:26 ging2 mysqld[9450]: 2017-07-06 22:32:26 140114825693312 [Warning] Can't create test file /home/mysql/ging2.lower-test
  Jul 06 22:32:26 ging2 mysqld[9450]: [87B blob data]
  Jul 06 22:32:26 ging2 mysqld[9450]: 2017-07-06 22:32:26 140114825693312 [ERROR] Aborting
  </code></pre>
  
  <p>I have no idea why it doesn't work and I think the permissions and ownership are the same as the old datadir.</p>
  
  <p>I think some of you guys know why. So could anyone help please?</p>
  
  <p>Thanks!! </p>