解决Linux-Centos7启动Mysql服务失败丢失mysql.sock问题

在新安装mysql后进行启动发现报错

mysql启动服务命令

systemctl start mysqld@3306

Starting mysqld (via systemctl):  Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld3306.service" and "journalctl -xe" for details.

按照错误提示信息进行排查

systemctl status mysqld3306.service

journalctl -xe

尝试连接mysql报错查看sock文件夹发现sock文件丢失

[root@cdh03 mysqldata3309]# mysql -uroot -S /data/mysqldata3309/sock/mysql.sock -p"Ygadb(vw<6ae"

mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/data/mysqldata3309/sock/mysql.sock' (2)

使用命令journalctl -xe查看报错具体原因，发现红色找字体的日志：SELinux is preventing mysqld from getattr access on the file /var/lib/mysql/ibdata1. For complete SELinux messages run: sealert -l
发现是selinux限制导致mysql服务启动失败

解决办法

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@cdh03 ~]# getenforce
Enforcing

1.2 /usr/sbin/sestatus

Current mode表示当前selinux防火墙的安全策略

[root@cdh03 ~]# /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@cdh03 ~]# setenforce 0
[root@cdh03 ~]# /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@cdh03 ~]# 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@cdh03 ~]# getenforce
Enforcing
重启
[root@cdh03 ~]# reboot
验证
[root@cdh03 ~]# /usr/sbin/sestatus
SELinux status: disabled

[root@cdh03 ~]# getenforce
Disabled

然后重启MYSQL服务，连接正常