操作系统：centos7
mysql版本：5.7.29
使用普通用户安装完成以后，启动mysql：
/data/mysql/usr/sbin/mysqld --defaults-file=/data/mysql/etc/my.cnf --user=dongzw &
日志中报：
[ERROR] Can't find error-message file '/usr/share/mysql/errmsg.sys'. Check error-message file location and 'lc-messages-dir' configuration directive.
大概搜索了一下，在my.cnf中添加
basedir=/data/mysql
再启动，报错变成了：
[ERROR] Can't read from messagefile '/data/mysql/share/mysql/errmsg.sys'
注意报错路径改变了，由/usr变成了/data，此时在安装路径下查找errmsg.sys文件：
[dongzw@localhost mysql]$ find /data/ -name errmsg.sys
/data/mysql/usr/share/mysql/bulgarian/errmsg.sys
/data/mysql/usr/share/mysql/czech/errmsg.sys
/data/mysql/usr/share/mysql/danish/errmsg.sys
/data/mysql/usr/share/mysql/dutch/errmsg.sys
/data/mysql/usr/share/mysql/english/errmsg.sys
.....................
看名字，应为各国语言的版本，这里选择english版本，新建并把文件拷到报错路径，当前路径为：/data/mysql
[dongzw@localhost mysql]$ mkdir -p share/mysql
[dongzw@localhost mysql]$ cp /data/mysql/usr/share/mysql/english/errmsg.sys share/mysql/
停止mysql：
/data/mysql/usr/bin/mysqladmin -uroot -proot -S /data/mysql/mysql.sock shutdown
再次启动，只有Warning信息了，问题解决。

解决方式2：
根据上面的查找到的errmsg.sys信息，可在my.cnf中配置：
lc-messages-dir=/data/mysql/usr/share/mysql/english
my.cnf中去掉basedir=/data/mysql
或者在启动命令加上--lc-messages-dir参数也可以解决问题：
/data/mysql/usr/sbin/mysqld --defaults-file=/data/mysql/etc/my.cnf --lc-messages-dir=/data/mysql/usr/share/mysql/english --user=dongzw &

附：安装5.7.29初始化数据库命令：
[dongzw@localhost data]$ /data/mysql/usr/sbin/mysqld --initialize --defaults-file=/data/mysql/etc/my.cnf --user=dongzw
如果报：
[ERROR] unknown variable 'defaults-file=/data/mysql/etc/my.cnf' 
[ERROR] Can't find error-message file '/usr/share/mysql/errmsg.sys'. Check error-message file location and 'lc-messages-dir' configuration directive.
需要把 --initialize放到--defaults-file后面
 /data/mysql/usr/sbin/mysqld  --defaults-file=/data/mysql/etc/my.cnf --initialize --user=dongzw

my.cnf简单配置文件：

# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html

[client]
port = 3306
socket = /data/mysql/mysql.sock
default-character-set = utf8

[mysqld]
port = 3306
character-set-server = utf8
#
# 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 leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# 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
basedir=/data/mysql
datadir=/data/mysql/data
socket=/data/mysql/mysql.sock

# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

log-error=/data/mysql/mysqld.log
pid-file=/data/mysql/mysqld.pid
secure-file-priv=/data/mysql/var/lib/mysql-files
explicit_defaults_for_timestamp=true