sudo pacman -S mysql
sudo mysqld --initialize --user=mysql --basedir=/usr --datadir=/var/lib/mysql
如果成功，terminal会出现：
2018-10-01T02:34:52.480465Z 0 [Warning] [MY-010915] [Server] 'NO_ZERO_DATE', 'NO_ZERO_IN_DATE' and 'ERROR_FOR_DIVISION_BY_ZERO' sql modes should be used with strict mode. They will be merged with strict mode in a future release.
2018-10-01T02:34:52.480614Z 0 [System] [MY-013169] [Server] /usr/bin/mysqld (mysqld 8.0.12) initializing of server in progress as process 11041
2018-10-01T02:35:27.030779Z 5 [Note] [MY-010454] [Server] A temporary password is generated for root@localhost:HA(pmD=en5b*
2018-10-01T02:35:52.397730Z 0 [System] [MY-013170] [Server] /usr/bin/mysqld (mysqld 8.0.12) initializing of server has completed
HA(pmD=en5b*就是临时产生的一个root用户的密码，需要登录进去重新更改才可以操作数据库。
先启动mysql服务：
sudo systemctl start mysqld
然后登录：
mysql -u root -p
更改root临时密码：
ALTER user 'root'@'localhost' IDENTIFIED BY 'new_password';
然后就可以各种命令了。
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