如何在 Ubuntu 16.04 上將 MySQL 資料目錄變更為另一個位置

$ mysql –u root –p
Output:
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 472
Server version: 5.6.30-0ubuntu0.14.04.1 (Ubuntu)
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>

Mysql> select @@datadir;
Output:
+-----------------+
| @@datadir       |
+-----------------+
| /var/lib/mysql/ |
+-----------------+
1 row in set (0.00 sec)

$ sudo systemctl stop mysql

$ sudo systemctl status mysql
Output:
mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Mon 2016-09-12 13:57:43 IST; 1s ago
   Process: 17669 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)
   Process: 17668 ExecStart=/usr/sbin/mysqld (code=exited, status=0/SUCCESS)
   Process: 17664 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
   Main PID: 17668 (code=exited, status=0/SUCCESS)
Sep 12 13:55:14 ubuntu-16 systemd[1]: Starting MySQL Community Server...
Sep 12 13:55:15 ubuntu-16 systemd[1]: Started MySQL Community Server.
Sep 12 13:57:40 ubuntu-16 systemd[1]: Stopping MySQL Community Server...
Sep 12 13:57:43 ubuntu-16 systemd[1]: Stopped MySQL Community Server.

$ rsync –av /var/lib/mysql /mnt/data_vol/
OutPut:
sending incremental file list
mysql/
mysql/auto.cnf
mysql/debian-5.7.flag
mysql/ib_buffer_pool
mysql/ib_logfile0
mysql/ib_logfile1
mysql/ibdata1
mysql/mysql/
mysql/mysql/columns_priv.MYD
mysql/mysql/columns_priv.MYI
mysql/mysql/columns_priv.frm
mysql/mysql/db.MYD
mysql/mysql/db.MYI
mysql/mysql/db.frm
mysql/mysql/db.opt
….
mysql/sys/x@0024user_summary.frmmysql/sys/x@0024user_summary_by_file_io.frm
mysql/sys/x@0024user_summary_by_file_io_type.frm
mysql/sys/x@0024user_summary_by_stages.frm
mysql/sys/x@0024user_summary_by_statement_latency.frm
mysql/sys/x@0024user_summary_by_statement_type.frm
mysql/sys/x@0024wait_classes_global_by_avg_latency.frm
mysql/sys/x@0024wait_classes_global_by_latency.frm
mysql/sys/x@0024waits_by_host_by_latency.frm
mysqlsys//x@0024waits_by_user_by_latency.frm
mysql/sys/x@0024waits_global_by_latency.frm
sent 199,384,083 bytes received 6,858 bytes 132,927,294.00 bytes/sec
total size is 199,307,568 speedup is 1.00

$ sudo mv /var/lib/mysql /var/lib/mysql_backup

$ sudo vi /etc/mysql/mysql.conf.d/mysqld.cnf
Output:
[mysqld_safe]
socket    = /var/run/mysqld/mysqld.sock
nice      = 0
[mysqld]
#
# * Basic Settings
#
user             = mysql
pid-file         = /var/run/mysqld/mysqld.pid
socket           = /var/run/mysqld/mysqld.sock
port             = 3306
basedir          = /usr
datadir          = /mnt/data_vol/mysql/
tmpdir           = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

$ sudo vi /etc/apparmor.d/tunables/alias
Output:
# ------------------------------------------------------------------
#
# Copyright (C) 2010 Canonical Ltd.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of version 2 of the GNU General Public
# License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
# Alias rules can be used to rewrite paths and are done after variable
# resolution. For example, if '/usr' is on removable media:
# alias /usr/ -> /mnt/usr/,
#
# Or if mysql databases are stored in /home:
# alias /var/lib/mysql/ -> /home/mysql/,
alias /var/lib/mysql/ -> /mnt/data_vol/mysql

$ sudo systemctl start mysql

$ sudo systemctl status mysql
Output:
mysql.service - MySQL Community Server
    Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
    Active: active (running) since Mon 2016-09-12 14:17:27 IST; 23s ago
   Process: 18481 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCC
   Process: 18477 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCES
  Main PID: 18480 (mysqld)
     Tasks: 28 (limit: 512)
    Memory: 137.3M
   CPU: 329ms
CGroup: /system.slice/mysql.service
        └─18480 /usr/sbin/mysqld
Sep 12 14:17:26 ubuntu-16 systemd[1]: Starting MySQL Community Server...
Sep 12 14:17:27 ubuntu-16 systemd[1]: Started MySQL Community Server.

$ mysql -uroot -p
Output:
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.13-0ubuntu0.16.04.2 (Ubuntu)
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select @@datadir
+----------------------+
| @@datadir            |
+----------------------+
| /mnt/data_vol/mysql/ |
+-----------------+
1 row in set (0.00 sec)
mysql>

$ sudo rm –rf /var/lib/mysql_backup