3.1 Processes, Services, and Packages

You can now move around, inspect, edit, and change permissions. Next, treat Linux as a running system: which programs are running? Is a service healthy? How is software installed?

Processes: running programs

Common commands:

ps aux
top
htop
pgrep -a nginx
kill -TERM 1234
kill -9 1234

ps gives a snapshot, top watches resources continuously, and pgrep finds processes by name. kill does not delete files; it sends signals to processes. Usually try TERM politely first and save KILL for last.

Package management

Different distribution families use different package managers:

Common flow:

sudo apt update
sudo apt install nginx
sudo apt remove nginx

update refreshes the package index. It does not upgrade every program. install installs software. On real servers, installing a service is usually only the first step; you still need to start it, inspect status, read logs, and confirm its port.

systemd services

Many Linux servers use systemd to manage long-running services:

systemctl status nginx
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl enable nginx
journalctl -u nginx -n 50

start runs a service now. enable makes it start automatically at boot. status shows current state, and journalctl shows service logs.

The next section continues with the surrounding skills: confirming that a network endpoint really responds, packaging files, passing configuration through environment variables, and keeping jobs running in the background or on a schedule.