Ubuntu16.04 修改mysql 数据存储目录datadir 启动失败 ，网上的各种方法都已经尝试，但是还是没有启动成功请教各位大神！！！！！
修改步骤
创建 迁移文件夹
cd /mnt
mkdir lib
cd lib && mkdir mysqldata
数据存放在 /mnt/lib/mysqldata
修改所属用户 和所属用户组为 msyql
sudo chown -vR mysql:mysql /mnt/lib/mysqldata
修改权限
sudo chmod -vR 700 /mnt/lib/mysqldata
迁移文件
停止服务
sudo /etc/init.d/mysql stop
迁移数据
cp -av /var/lib/mysql/* /mnt/lib/mysqldata
vim /etc/mysql/mysql.conf.d/mysqld.cnf
将 [mysqld] 组下的 datadir改为：
datadir = /mnt/lib/mysqldata
sudo vim /etc/apparmor.d/usr.sbin.mysqld
找到其中的
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,
两行权限声明，可以在前面加上#好注释掉。然后对照格式，加入新路径的权限声明：
/mnt/lib/mysqldata/ r,
/mnt/lib/mysqldata/** rwk
重启服务
配置文件修改成功后就可以重启数据库，重启数据库之前需要先重新载入apparmor配置文件，使用下面命令重新载入：
sudo /etc/init.d/apparmor restart
sudo /etc/init.d/mysql start
重启的时候
Starting mysql (via systemctl): mysql.serviceJob for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
failed!
root@iZm5e472vz1trxejt8m5akZ:/etc/mysql# systemctl status mysql.service
● mysql.service - MySQL Community Server
Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2018-06-23 00:55:37 CST; 25s ago
Process: 13418 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)
Process: 13408 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
Main PID: 13417 (mysqld)
CGroup: /system.slice/mysql.service
└─13417 /usr/sbin/mysqld
. 配置文件 内容
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
[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 = /var/lib/mysql
datadir = /mnt/lib/mysqldata
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address = 0.0.0.0
#
# * Fine Tuning
#
key_buffer_size = 16M
max_allowed_packet = 16M
thread_stack = 192K
thread_cache_size = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover-options = BACKUP
#max_connections = 100
#table_cache = 64
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 1M
query_cache_size = 16M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file = /var/log/mysql/mysql.log
#general_log = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#log_slow_queries = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
#server-id = 1
#log_bin = /var/log/mysql/mysql-bin.log
expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
