在Ubuntu 18.04上lower_case_table_names = 1不允许mysql启动

Question

我在ubuntu 18.04上安装了mysql社区服务器8.013，并且遇到以下问题。我想设置lower_case_table_names = 1，以便在数据库中使用不区分大小写的表名。我编辑了/etc/mysql/mysql.conf.d/mysqld.cnf，并在[mysqld]下添加了以下行

lower_case_table_names=1

mysqld.cnf现在如下

[mysqld]
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
datadir         = /var/lib/mysql
log-error       = /var/log/mysql/error.log
lower_case_table_names=1

我停止了使用

sudo service mysql stop

然后我尝试使用重新启动

sudo service mysql start

但我收到以下错误

Job for mysql.service failed because the control process exited with error code.
See "systemctl status mysql.service" and "journalctl -xe" for details.

我试过了

systemctl status mysql.service

我得到了以下信息

christoph@christoph-Latitude-E6530:/etc/init.d$ systemctl status mysql.service
? mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Thu 2018-11-01 16:38:14 EET; 24s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 6681 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
  Process: 6642 ExecStartPre=/usr/share/mysql-8.0/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 6681 (code=exited, status=1/FAILURE)
   Status: "SERVER_BOOTING"
    Error: 2 (No such file or directory)

??? 01 16:38:12 christoph-Latitude-E6530 systemd[1]: Starting MySQL Community Server...
??? 01 16:38:14 christoph-Latitude-E6530 systemd[1]: mysql.service: Main process exited, code=exited, status=1/FAILURE
??? 01 16:38:14 christoph-Latitude-E6530 systemd[1]: mysql.service: Failed with result 'exit-code'.
??? 01 16:38:14 christoph-Latitude-E6530 systemd[1]: Failed to start MySQL Community Server.

使用journalctl -xe我得到以下信息

-- The result is RESULT.
??? 01 17:32:00 christoph-Latitude-E6530 sudo[2526]: pam_unix(sudo:session): session closed for user root
??? 01 17:32:04 christoph-Latitude-E6530 wpa_supplicant[743]: wlp3s0: WPA: Group rekeying completed with 4c:5e:0c:7a:95:cf [GTK=CCMP]
??? 01 17:32:08 christoph-Latitude-E6530 gnome-shell[1565]: Some code accessed the property 'discreteGpuAvailable' on the module 'appDisplay'. That property w
??? 01 17:32:08 christoph-Latitude-E6530 gnome-shell[1565]: Some code accessed the property 'WindowPreviewMenuItem' on the module 'windowPreview'. That proper
lines 1349-1371/1371 (END)
??? 01 17:31:58 christoph-Latitude-E6530 systemd[1]: Starting MySQL Community Server...
-- Subject: Unit mysql.service has begun start-up
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- Unit mysql.service has begun starting up.
??? 01 17:31:58 christoph-Latitude-E6530 audit[2593]: AVC apparmor="STATUS" operation="profile_replace" info="same as current profile, skipping" profile="unconfined" name="/usr/sbin/mysqld" pid=2593 comm=
??? 01 17:31:58 christoph-Latitude-E6530 kernel: kauditd_printk_skb: 28 callbacks suppressed
??? 01 17:31:58 christoph-Latitude-E6530 kernel: audit: type=1400 audit(1541086318.959:39): apparmor="STATUS" operation="profile_replace" info="same as current profile, skipping" profile="unconfined" name
??? 01 17:32:00 christoph-Latitude-E6530 systemd[1]: mysql.service: Main process exited, code=exited, status=1/FAILURE
??? 01 17:32:00 christoph-Latitude-E6530 systemd[1]: mysql.service: Failed with result 'exit-code'.
??? 01 17:32:00 christoph-Latitude-E6530 systemd[1]: Failed to start MySQL Community Server.
-- Subject: Unit mysql.service has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- Unit mysql.service has failed.

我也尝试使用启动服务器

sudo service mysql start --initialize lower_case_table_names=1

如这里描述的 lower_case_table_names MySQL 8.0.12中的设置， 但是我仍然遇到相同的错误，并且mysql根本无法启动

如果我运行以下

sudo vi /var/log/mysql/error.log

我得到以下错误原因

Different lower_case_table_names settings for server ('1') and data dictionary ('0').
Data Dictionary initialization failed.

有什么想法为什么会发生以及如何解决？

Answer 1

这在带有 MySQL 8.0.20 的全新 Ubuntu Server 20.04 安装上对我有用（没有现有的数据库需要关心 - 因此如果您有重要数据，那么您应该在执行此操作之前将其备份/导出到其他地方）：

所以......我做了所有具有提升权限的事情：

sudo su

安装 MySQL（如果尚未安装）：

apt-get install mysql-server

备份配置文件，卸载，删除所有数据库和MySQL相关数据：

cp /etc/mysql/mysql.conf.d/mysqld.cnf /etc/mysql/mysql.conf.d/mysqld.cnf.backup
service mysql stop
apt-get --purge autoremove mysql-server
rm -R /var/lib/mysql

恢复保存的配置文件，编辑文件（在 [mysqld] 行下添加一行）：

cp /etc/mysql/mysql.conf.d/mysqld.cnf.backup /etc/mysql/mysql.conf.d/mysqld.cnf
vim /etc/mysql/mysql.conf.d/mysqld.cnf

...
lower_case_table_names=1
...

重新安装 MySQL（保留配置文件），配置其他设置：

apt-get install mysql-server
service mysql start
mysql_secure_installation
mysql

SHOW VARIABLES LIKE 'lower_case_%';
exit

Answer 2

为了使此功能在MySQL 8.0和linux中遵循以下步骤

0）使用以下命令执行以下步骤之前，请备份mysql模式：

mysqldump  -h localhost -u root -p mysql > /home/username/dumps/mysqldump.sql

然后使用停止mysql

sudo service mysql stop

1）移动或删除/ var / lib / mysql目录。这将删除所有数据库！

mv /var/lib/mysql /tmp/mysql

2）创建一个新的/ var / lib / mysql目录，并使mysql用户成为所有者

mkdir /var/lib/mysql
chown -R mysql:mysql /var/lib/mysql
chmod 750 /var/lib/mysql

3）编辑/etc/mysql/mysql.conf.d/mysqld.cnf并在[mysqld]之后添加以下行

lower_case_table_names=1

4）使用以下命令初始化mysql

mysqld --defaults-file = / etc / mysql / my.cnf --initialize lower_case_table_names = 1 --user = mysql --console

用默认文件的实际位置更改默认文件。有关mysql初始化的更多信息，请访问：https : //dev.mysql.com/doc/refman/8.0/en/data-directory-initialization-mysqld.html

5）（可选）重复

chown -R mysql:mysql /var/lib/mysql
chmod 750 /var/lib/mysql

如果/ var / lib / mysql中文件的所有者不是mysql

6）使用启动mysql

sudo service mysql start

7）如果一切正常，请使用

mysql -u root -p

并通过运行此查询

SHOW VARIABLES where Variable_name like 'lower%';

你会得到

'lower_case_table_names', '1'

8）使用在步骤0中创建的转储来还原mysql模式。

9）执行mysql_upgrade创建sys模式