执行xfs_repair /dev/mapper/centos-root 或者xfs_repair /dev/mapper/centos-root -L

# xfs_repair /dev/mapper/centos-root -L
# reboot

$arr=[0,1,2,3];
$newArr = array_map(function ($value){
    return 'str_'.$value;
},$arr);


$newArr就变成了['str_0','str_1','str_2','str_3']

SELECT * FROM tb_item AS T WHERE 1>(
 SELECT COUNT(id) 
 FROM tb_item WHERE
`item_category_id`=T.`item_category_id` AND id>T.id) 

导入数据

mysql -utest -p demo < demo.sql

导出数据

/usr/local/mysql/bin/mysqldump -uroot -p demo > demo.sql

CentOS 8 换源，设置dnf / yum镜像
aliyun更新了centos8的说明

curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-8.repo

centos 8 默认是会读取centos.org的mirrorlist的，所以一般来说是不需要配置镜像的。
如果你的网络访问centos.org的mirrorlist有问题，可能才需要另外配置镜像

cd /etc/yum.repos.d

备份

cp CentOS-Base.repo CentOS-Base.repo.bak
cp CentOS-AppStream.repo CentOS-AppStream.repo.bak
cp CentOS-Extras.repo CentOS-Extras.repo.bak

sed -i 's/mirrorlist=/#mirrorlist=/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo
sed -i 's/#baseurl=/baseurl=/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo
sed -i 's/http:\/\/mirror.centos.org/https:\/\/mirrors.aliyun.com/g' CentOS-Base.repo CentOS-AppStream.repo CentOS-Extras.repo

内容摘自 csdn