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This article mainly explains "what is the limitation of ulimit on system resources in linux system". The content of the explanation in this article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the limitation of ulimit on system resources in linux system".

Limitations of file systems and programs: ulimit

Ulimit restricts some system resources of users

Including the number of files that can be opened

Available CPU time

The total amount of memory that can be used, etc.

[root@www ~] # ulimit [- acdfHlmnpsStvw] [size]

Options and parameters:

-H: hard limit, strict setting, must not exceed this setting value

-S: soft limit, the warning setting can exceed this setting value, but if it exceeds, there is a warning message.

-a: all limits can be listed without any options or parameters.

-c: when an error occurs in some program, the system may write the program's information in memory into a file, which is called the core file.

-f: the maximum file capacity that can be created by this shell (generally set to 2GB) is in Kbytes

-d: maximum broken memory (segment) capacity that can be used by the program

-l: the amount of memory available for locking (lock)

-m: sets the maximum amount of resident memory that can be used. Unit: kbytes

-n: sets the maximum value of file descriptors that the kernel can open at the same time. Unit: n

-p: sets the maximum value of the pipe buffer. Unit: kbytes

-s: sets the maximum value of the stack. Unit: kbytes

-v: sets the maximum value of virtual memory. Unit: kbytes

-t: maximum CPU time that can be used (in seconds)

-u: the maximum number of programs (process) that a single user can use

General simple setting: ulimit-SHn 65535

Make it permanent:

[root@www ~] # vi / etc/security/limits.conf

* soft noproc 65535

* hard noproc 65535

* soft nofile 409600

* hard nofile 409600

* stands for all users

Noproc represents the maximum number of processes

Nofile represents the maximum number of file openings

Case study of production environment:

[root@www ~] # vi / etc/security/limits.conf

# End of file

* soft core unlimit

* hard core unlimit

* soft fsize unlimited

* hard fsize unlimited

* soft data unlimited

* hard data unlimited

* soft nproc 65535

* hard nproc 63535

* soft stack unlimited

* hard stack unlimited

* soft nofile 409600

* hard nofile 409600

857 cat / etc/security/limits.conf

858 cat / etc/security/limits.d/90-nproc.conf

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