当我尝试在ubuntu 20.04机器上执行以下命令来安装mysql 5.7时，出现以下错误。我在安装mysql时遵循了这里的文档https://computingforgeeks.com/how-to-install-mysql-on-ubuntu-focal/。
第一个

/etc/mysql/my.cnf文件只有以下几行，其他行都被注解掉了，它是默认文件。

!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mysql.conf.d/

当我检查**/etc/mysql/conf.d/**目录时，发现了以下文件。

mysql.cnf

[mysql]

mysqldump.cnf文件系统

[mysqldump]
quick
quote-names
max_allowed_packet  = 16M

当我检查**/etc/mysql/mysql.conf.d/**目录时，下面的文件在那里。

我的网址.cnf

[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

# By default we only accept connections from localhost

bind-address    = 127.0.0.1

# Disabling symbolic-links is recommended to prevent assorted security risks

symbolic-links=0

/etc/my.cnf文件如下所示。

basedir=/var/lib/mariadb/mysql
datadir=/var/lib/mariadb
user=mysql