Seeing and controlling what runs.
WHAT A PROCESS IS
A running program, with an identifier.
WHAT ps DOES
Lists processes, as a snapshot.
WHAT THE COMMON FORM SHOWS
Every process, with user, resource use and command.
WHAT top AND htop DO
Show processes updating continuously, ordered by consumption.
WHAT TO LOOK AT FIRST
Which process is using the most processor or memory.
WHAT LOAD AVERAGE MEANS
The average number of processes waiting to run, over one, five and fifteen minutes.
HOW TO INTERPRET IT
Compare it to the number of processor cores.
WHAT A LOAD ABOVE THE CORE COUNT MEANS
Work is queuing.
WHY THE THREE FIGURES MATTER
They show direction: rising, falling, or sustained.
WHAT kill DOES
Sends a signal to a process.
WHAT THE DEFAULT SIGNAL ASKS
That the process shut down cleanly.
WHAT SIGNAL NINE DOES
Terminates immediately, with no chance to clean up.
WHY TO AVOID IT INITIALLY
It can leave corrupt files and stale locks.
WHAT TO TRY FIRST
The default, then wait.
WHAT pkill AND killall DO
Match by name rather than identifier.
WHY THEY DESERVE CARE
A loose pattern kills more than intended.
