解决Linux-Centos7启动Mysql服务失败

启动mysql服务的时候service mysqld start报错了

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

                                                           [失败]

使用命令journalctl -xe查看报错具体原因，发现鲜红的日志：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限制了。

解决方法如下：

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 ~]# getenforce
  Enforcing

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

重新启动mysqld，结果还是失败，使用命令systemctl status mysqld.service查看，提示Failed to start SYSV 

                MySQL服务在启动的时候，不能创建pid文件。

mkdir -p /var/run/mysqld/

chown mysql.mysql /var/run/mysqld/

即可