Difference between sysctl options to set system parameters

Question

I see on the web two different commands to load sysctl custom parameters:

• sysctl --system
• sysctl -p

Is there any difference between the two commands? I know the second one I posted can take the path of a file to load but without any file specified, everything will be loaded.

Answer 1

The sysctl --system load settings from all configuration files.

The sysctl -p will load settings from the default /etc/sysctl.conf.

man sysctl:

 -p[FILE], --load[=FILE]
 Load in sysctl settings from the file specified or /etc/sysctl.conf if none given. Specifying - as filename means
 reading data from standard input. Using this option will mean arguments to sysctl are files, which are read in the
 order they are specified. The file argument may be specified as regular expression.
 --system
 Load settings from all system configuration files. Files are read from directories in the following list in given
 order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent direc‐
 tories is ignored.
 /etc/sysctl.d/*.conf
 /run/sysctl.d/*.conf
 /usr/local/lib/sysctl.d/*.conf
 /usr/lib/sysctl.d/*.conf
 /lib/sysctl.d/*.conf
 /etc/sysctl.conf

• MC68020: Perhaps you could explain the reasons for (what purpose would serve) configuration files different from default.