Notes for modifying ulimit in Linux

If you encounter a similar error message
Ulimit: Max user processes: cannot modify limit: The operation is not allowed.
Ulimit: open files: cannot modify limit: operation not allowed

Why is it possible for root users? Why do common users encounter this problem?
Take a look at/etc/security/limits. conf and you will probably understand it.
Linux has default ulimit restrictions on users. This file can be used to configure users' hard configuration and soft configuration. Hard configuration is an upper limit.
If the modification exceeds the upper limit, an error such as "operation not allowed" will occur.

Add
* Soft noproc 10240
* Hard noproc 10240
* Soft nofile 10240
* Hard nofile 10240
Limit the maximum number of threads and files of any user to 10240.