Limit related content settings in Linux

Limit related content settings in Linux

The Linux operating system is a free and open source operating system that is widely used in servers and embedded systems. In Linux, sometimes we need to set some restrictions on certain processes or users to avoid resource abuse and system performance degradation. This article will introduce the settings of Limit-related content in Linux and provide some specific code examples.

1. Introduction to Limit-related concepts
In Linux, we can use Limit-related settings to limit the resources available to processes or users, including the number of processes, memory, CPU usage, etc. Commonly used Limit-related setting tools include PAM (PAM, Pluggable Authentication Modules) and ulimit (ulimit system call).

PAM is a method that allows system administrators to provide a single login authentication method for different applications or services. By configuring PAM, we can set limits on the number of failed logins, login timeout, etc.

ulimit is a command that can set process resource limits. The ulimit command can set resource limits that a process can use, including CPU time, file size, number of processes, etc.

2. Examples of Limit-related settings
Now let’s take a closer look at some common Limit-related settings and corresponding code examples.

1. Set the limit on the number of open files
   The limit on the number of open files is a very important limit. In some application scenarios, a large number of file descriptors may need to be opened to handle concurrent requests. By setting a limit on the number of open files, you can ensure that the system can run normally.

Code example:
Open the /etc/security/limits.conf file and add the following content:

• soft nofile 65535
• hard nofile 65535

The 65535 here represents the maximum number of file descriptors. We set the soft limit and hard limit by setting the soft and hard options respectively. The soft limit is a warning value. When this limit is exceeded, the system will give a warning. The hard limit is the actual limit on the number of files opened.

2. Set process number limit
   In some cases, it may be necessary to limit the number of processes for a certain user or a certain process group to avoid excessive resource usage.

Code example:
Open the /etc/security/limits.conf file and add the following content:

• soft nproc 1000
• hard nproc 2000

nproc here represents the limit on the number of processes. We set the soft limit and hard limit by setting the soft and hard options respectively. The soft limit is a warning value. The system will give a warning when this limit is exceeded. The hard limit is the actual limit on the number of processes.

3. Set CPU time limit
   In some cases, it may be necessary to limit the CPU usage time of a certain user or a certain process to prevent a certain process from excessively occupying CPU resources.

Code example:
Set the CPU time limit through the ulimit command:

ulimit -t 60

The 60 here represents the CPU time limit, the unit is Second.

4. Set memory limit
   In some cases, it may be necessary to limit the memory usage of a user or a process to prevent excessive system memory usage.

Code example:
Set the memory limit through the ulimit command:

ulimit -m 102400

The 102400 here represents the memory limit, in KB.

3. Summary
This article introduces the settings of Limit-related content in Linux and provides some specific code examples. By setting Limit appropriately, we can limit the resources available to processes or users and ensure system stability and performance.

In actual applications, we can set the appropriate Limit value according to specific needs and situations. However, it should be noted that too strict restrictions may cause the application to fail to run properly, so the pros and cons should be weighed based on the actual situation.

I hope this article will help you understand the setting of Limit-related content in Linux. I also hope that readers can set Limit appropriately according to their own needs to obtain a better user experience.

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