prlimit

Charles is a RHEL Sysadmin at Red Hat. He needs to demonstrate the prlimit command for a group of junior engineers. Please list and explain several examples.

Certainly! Here are several examples of how Charles can demonstrate the prlimit command to the group of junior engineers:

  1. Show the resource limits for the current user:
    • prlimit --pid $$ --nofile

    • This command displays the current user's resource limits for the number of open file descriptors. The $$ represents the process ID of the current shell.

  2. Set the maximum number of open file descriptors for a specific process:
    • prlimit --pid <pid> --nofile=500
    • This command sets the maximum number of open file descriptors for the specified <pid> to 500. It restricts the number of files that process can have open simultaneously.
  3. Display the maximum stack size limit for a process:
    • prlimit --pid <pid> --stack
    • This command shows the maximum stack size limit for the specified <pid>. It indicates the amount of stack memory a process can use.
  4. Set the maximum number of processes for a specific user:
    • prlimit --nproc=100:200 --uid <uid>
    • This command limits the maximum number of processes a specific user, identified by <uid>, can create to a range of 100 to 200. It controls the number of concurrent processes that user can initiate.
  5. Show the maximum resident set size (physical memory) for a process:
    • prlimit --pid <pid> --rss
    • This command restricts the maximum amount of CPU time a specific user, identified by <uid>, can consume to a range of 2 to 4 seconds. It controls the CPU usage of that user's processes.

By demonstrating these example commands, Charles can showcase the versatility of the prlimit command and its ability to manage various resource limits on a RHEL system. This will help the junior engineers understand how to control resource allocation and optimize system performance.