Linux – Which process is `/proc/self/` for

CPULimit is exactly what you need. You start the program, then run cpulimit against the program name or PID, specifying what percentage you want it limited.

The following command limits the process at PID 7777 to 5% CPU usage.

cpulimit -p 7777 -l 5

Alternatively, you can use the name of the executable:

cpulimit -e myprogram -l 5

Or the absolute path of the executable:

cpulimit -P /path/to/myprogram -l 5

Note the percentage is of all cores; so if you have 4 cores, you could use 400%.

A foreground process does not necessitate user interaction. You can do

cp very_large_file destination

and this would block your terminal until the copy finished and would be considered a foreground process with no user interaction. The point here being whether the process blocks the execution of other processes until it terminates.

Two ways you can make a foreground process into a background one:

1- Adding an ampersand (&) at the end of your command line:

cp very_large_file destination &

2- Stopping a foreground process then bringing it into the background:

cp very_large_file destination

CTRL+Z

bg

Now apache2 would definitely count as a background process: yes you can interact with it via http requests but it simply listens on port 80 (by default) waiting for such a request: it does not block the system until the user makes a request.

And why do you take issue at most processes being considered background processes? This is indeed normal in a "multi-tasking operating system".