What is the use of these directories in a Linux filesystem

Hello everyone

There are some directories in the Linux root directory that are always not much talked of or whose functionality is not well explained. Therefore, I would like to know the use of the following directories in the root directory and the files that they contain, how to use them on the system especially if one is a system administrator:

  • /opt

  • /srv

  • /run

  • /sys

And how can i limit the size of user home directories in the /home directory to a certain amount.

/sys This directory is similar to /proc in that it provides a device and system interface.
/opt This may contain additional third-party software. Many systems don’t use /opt.
/srv contains site-specific data which is served by this system.
/run Run-time variable data: Information about the running system since last boot, e.g., currently logged-in users and running daemons.


How Linux Works (Book)


And any ideas on how to limit user home directory size?


Use disk quota for limiting users home directory