SELinux(Security-Enhanced Linux) 是美国国家安全局（NSA）对于强制访问控制的实现，是 linux历史上最杰出的新安全子系统。但是我们一般都不用它，因为它管的东西太多了，想做安全可以用防火墙等其他措施。 
我们可以通过查看配置文件的命令 cat /etc/selinux/config 来查看状态，

[root@mazhonghua ~]# 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
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted 

发现SELinux共有3个状态enforcing （执行中）、permissive （不执行但产生警告）、disabled（关闭）。  我们可以通过修改配置文件来修改SELinux的状态

[root@mazhonghua ~]# sed -i s#SELINUX=enforcing#SELINUX=disabled# /etc/selinux/config 
[root@mazhonghua ~]# 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=disabled
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted 

最后我们重启服务器，SELinux状态由enforcing变为disabled 。  当然，一般我们的Linux都不能重启，我们可以使用这个命令 setenforce 1 临时（重启即失效）设置SELinux 成为enforcing模式（setenforce 0 设置SELinux 成为permissive模式），用getenforce这个命令来检查。

root@mazhonghua ~]# setenforce 0
[root@mazhonghua ~]# getenforce 
Permissive

我们还可以用 /usr/sbin/sestatus 命令来查看SELinux的状态。

[root@mazhonghua ~]# /usr/sbin/sestatus 
SELinux status:                 enabled
SELinuxfs mount:                /selinux
Current mode:                   enforcing
Mode from config file:          disabled
Policy version:                 24
Policy from config file:        targeted