Mysql
启动测试：
# systemctl status mysqld.service
查看日志：
tail -n 200 /var/log/mysqld.log
2018-08-10T02:24:04.877063Z 0 [Warning] Can't create test file /data/mysql/VM_129_126_centos.lower-test
2018-08-10T02:24:04.906042Z 0 [ERROR] InnoDB: The innodb_system data file 'ibdata1' must be writable
日志
设置权限：
[root@VM_129_126_centos mysql]# sudo chmod 777 /data/mysql/
再次测试：
重启：
mysqld restart --user=root
=================================================================================
create database jnshu default charset utf8;
停止
service mysqld stop
启动服务
service mysqld start
重启
service mysqld restart
mysqld --initialize --user=root
mysqld --user=root
mysqld restart --user=root
mysqld --skip-grant-tables
重启服务器
"jdbc:mysql://119.29.17.188/jnshu?useUnicode=true&characterEncoding=UTF-8&useSSL=false&rewriteBatchedStatements=true";
日志：
vim /var/log/mysqld.log
tail -n 100 /var/log/mysqld.log
Packet for query is too large (12238 > 1024). You can change this value
show VARIABLES like '%max_allowed_packet%';
set global max_allowed_packet = 2*1024*1024*10
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)
ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1' (111)
Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (111)
删除 /var/lib/mysql/mysql.sock
重新mysql -uroot -p
提示：
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
停止
service mysqld stop
启动服务
service mysqld start
提示：
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details
使用：
mysqld --user=root
重新连接
查看：
systemctl status mysqld.service
journalctl -xe
Can't create test file /data/mysql/VM_129_126_centos.lower-test
vi /etc/selinux/config
摘抄：
下面为转：
本文永久更新链接地址：http://www.linuxidc.com/Linux/2016-11/137723.htm
1. 查看SELinux状态
1.1 getenforce
- getenforce 命令是单词get（获取）和enforce(执行)连写，可查看selinux状态，与setenforce命令相反。
-
setenforce 命令则是单词set（设置）和enforce(执行)连写，用于设置selinux防火墙状态，如： setenforce 0用于关闭selinux防火墙，但重启后失效[root@localhost ~]# getenforceEnforcing
1.2 /usr/sbin/sestatus
Current mode表示当前selinux防火墙的安全策略
[root@localhost ~]# /usr/sbin/sestatus
SELinux status: enabled
SELinuxfs mount: /sys/fs/selinux
SELinux root directory: /etc/selinux
Loaded policy name: targeted
Current mode: enforcing
Mode from config file: enforcing
Policy MLS status: enabled
Policy deny_unknown status: allowed
Max kernel policy version: 28
SELinux status：selinux防火墙的状态，enabled表示启用selinux防火墙
Current mode： selinux防火墙当前的安全策略，enforcing 表示强
2. 关闭SELinux
2.1 临时关闭
setenforce 0 ：用于关闭selinux防火墙，但重启后失效。
[root@localhost ~]# setenforce 0
[root@localhost ~]# /usr/sbin/sestatus
SELinux status: enabled
SELinuxfs mount: /sys/fs/selinux
SELinux root directory: /etc/selinux
Loaded policy name: targeted
Current mode: permissive
Mode from config file: enforcing
Policy MLS status: enabled
Policy deny_unknown status: allowed
Max kernel policy version: 28
2.1 永久关闭
修改selinux的配置文件，重启后生效。
打开 selinux 配置文件
[root@localhost ~]# vim /etc/selinux/config
修改 selinux 配置文件
将SELINUX=enforcing改为SELINUX=disabled，保存后退出
# This file controls the state of SELinux on the system.# SELINUX= can take one of these three values:# enforcing - SELinux security policy is enforced.# permissive - SELinux prints warnings instead of enforcing.# disabled - No SELinux policy is loaded.SELINUX=enforcing
# SELINUXTYPE= can take one of three two values:# targeted - Targeted processes are protected,# minimum - Modification of targeted policy. Only selected processes are protected. # mls - Multi Level Security protection.SELINUXTYPE=targeted
此时获取当前selinux防火墙的安全策略仍为Enforcing，配置文件并未生效。
[root@localhost ~]# getenforce
Enforcing
重启
[root@localhost ~]# reboot
验证
[root@localhost ~]# /usr/sbin/sestatus
SELinux status: disabled
[root@localhost ~]# getenforce
Disabled
