Understand the different working modes of SELinux

SELinux is a security-enhanced Linux. Its full name is Security-Enhanced Linux, which is a security module of the Linux kernel. It can provide mandatory access control function, through which the security of the system can be better protected. SELinux can effectively prevent malicious programs from abusing system resources by controlling the permissions of processes to access resources.

In SELinux, there are three working modes: Enforcing, Permissive and Disabled. The following will introduce these three working modes in detail and provide specific code examples.

1. Enforcing mode
   Enforcing mode is the default working mode of SELinux. In this mode, SELinux enforces policy and blocks policy violations. If a process attempts to perform an unauthorized operation, SELinux blocks the operation and generates an appropriate alert. In Enforcing mode, system administrators can view and analyze SELinux alarm logs and update SELinux policies as needed.

   The following is a simple code example that demonstrates how to view the current SELinux working mode and set it to Enforcing mode:

   # 查看当前SELinux模式
   getenforce
   
   # 将SELinux设置为Enforcing模式
   setenforce 1

2. Permissive mode
   Permissive mode It is a working mode of SELinux. Compared with Enforcing mode, Permissive mode does not enforce the policy, but only records violations of the policy and generates warnings. In this mode, system administrators can view SELinux alert logs, but unauthorized operations will not be blocked. Permissive mode is usually used to debug and analyze SELinux's policies so that adjustments can be made without affecting the normal operation of the system.

   The following is a simple code example that demonstrates how to set SELinux to Permissive mode:

   # 将SELinux设置为Permissive模式
   setenforce 0

3. Disabled mode
   Disabled mode is one of the working modes of SELinux , which will completely disable the functionality of SELinux. In this mode, the system will not execute any SELinux policies and will not generate any alarms. Generally speaking, it is not recommended to set SELinux to Disabled mode because this will reduce the security of the system.

   The following is a simple code example that demonstrates how to set SELinux to Disabled mode:

   # 将SELinux设置为Disabled模式
   setenforce 0

In summary, SELinux has three working modes: Enforcing, Permissive and Disabled. System administrators can choose a suitable working mode as needed to ensure system security and stability. In actual applications, you can choose the appropriate mode according to the specific situation, and adjust the SELinux policy as needed to improve the security and reliability of the system.

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