centos7数据库连接使用127.0.0.1报permission denied，使用localhost报No such file or directory

安装lamp环境后，测试数据库连接。

当host使用127.0.0.1时，报错：(HY000/2002): Permission denied。

把host换成localhost后，又报错：SQLSTATE[HY000] [2002] No such file or directory。

最后发现是因为没有关闭selinux，通常情况下载安装完CentOS7后，默认情况下SElinux是启用状态。

[root@rdo ~]# 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

如果要临时关闭，可以执行：

setenforce 0

此时状态如下：

[root@rdo ~]# 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    

如果要永久关闭，可以修改配置文件/etc/selinux/config，将SELINU置为disabled。

[root@rdo ~]# cat /etc/selinux/config   
  
# 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  
SELINUX=disabled  
# 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  

修改该配置文件也可以执行下面的命令来完成：

sed -i '/SELINUX/s/enforcing/disabled/' /etc/selinux/config 

修改完成后，保存重启，重启后状态如下：

[root@rdo ~]# sestatus  
SELinux status:                 disabled