（1）如果之前安装了Mysql，卸载后重新安装Mysql启动后可能会发生/var/log/mysqld.sql中没有默认密码生成的问题，此时可以删除/var/lib/mysql 整个文件夹，然后重启mysqld服务就可以让整个数据库重新初始化并在/var/log/mysqld.log中生成默认密码了。
查看mysql数据库文件存放路径：
mysql> show global variables like "%datadir%";
查看MySQL安装目录
ps -ef|grep mysql
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/8.0/en/server-configuration-defaults.html
[mysqld]
# skip-grant-tables
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove the leading "# " to disable binary logging
# Binary logging captures changes between backups and is enabled by
# default. It's default setting is log_bin=binlog
# disable_log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
#
# Remove leading # to revert to previous value for default_authentication_plugin,
# this will increase compatibility with older clients. For background, see:
# https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_default_authentication_plugin
# default-authentication-plugin=mysql_native_password
#sql_mode="MYSQL40"
sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'
default_authentication_plugin=mysql_native_password
# datadir=/var/lib/mysql
# socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysqld.log
################# 停止mysqld服务 #####################
[root@localhost ~]# service mysqld stop
Redirecting to /bin/systemctl stop mysqld.service
[root@localhost ~]#
########### 创建新的mysql数据存放路径 #################
[root@localhost ~]# mkdir -p /home/data/
[root@localhost ~]# ls /home/data/
[root@localhost ~]#
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/8.0/en/server-configuration-defaults.html
[mysqld]
# skip-grant-tables
#
# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M
#
# Remove the leading "# " to disable binary logging
# Binary logging captures changes between backups and is enabled by
# default. It's default setting is log_bin=binlog
# disable_log_bin
#
# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M
#
# Remove leading # to revert to previous value for default_authentication_plugin,
# this will increase compatibility with older clients. For background, see:
# https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_default_authentication_plugin
# default-authentication-plugin=mysql_native_password
#sql_mode="MYSQL40"
sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'
default_authentication_plugin=mysql_native_password
# datadir=/var/lib/mysql
# socket=/var/lib/mysql/mysql.sock
datadir=/home/data/mysql
socket=/home/data/mysql/mysql.sock
log-error=/var/log/mysqld.log
如上所示，修改了datadir=/home/data/mysql, socket=/home/data/mysql/mysql.sock
[root@localhost ~]# mv /var/lib/mysql /home/data/
[root@localhost ~]# ls /home/data/mysql/
auto.cnf ca.pem client-key.pem ibdata1 ib_logfile1 performance_schema public_key.pem server-key.pem test
ca-key.pem client-cert.pem ib_buffer_pool ib_logfile0 mysql private_key.pem server-cert.pem sys
[root@localhost ~]#
注意：我这使用了mv来移动mysql文件夹，请保持一致
参考：https://blog.csdn.net/zgrjkflmkyc/article/details/105571586